It is the pursuit of this pallid flame, of the crisp, clear fire it burns within us, that makes us lift the glass of tequila to our lips and to savour the rare fragrance it imparts.

Don't run into your local liquor store or market hoping to quickly grab a bottle or two of sipping tequila - not if your purchase is being motivated by a desire for quality, variety and distinction. Even if price is no object, what you will find, is quite literally staggering. There are over 600 different brands of tequila currently on the market. If you thought choosing the right wine was difficult, watch out! At least most of us know what kind of wine to combine with certain types of food, and have a basic understanding of the most common varietals.

As you peruse the shelves lined with every conceivable type and price of tequila, you may find yourself in an internal argument. Will paying $200.00 plus for a fancy bottle really spell the difference between an unforgettable tasting experience, or will it be just an unforgettably expensive experience? Or, can you pay a reasonable price, say between $30.00 and $75.00, and still enjoy a bottle whose name will leap from your lips whenever asked for a suggestion on a good bottle of tequila?

With these questions in mind it behooves you to take a bit of time, before you hit the market, to understand some of the components that make one tequila different from the next. Most elemental, is the production process. This includes everything from how each distiller bakes the agave, ferments the juice, ages and blends the final product - plus how long each takes. But growing techniques, soil, climate, altitude of the fields, age of the agave when harvested, the type of equipment and other factors also influence the result. Perhaps the most critical difference is between 100% agaves and those made with sugars (mixto). Simply put, the 100% agave products are better in all aspects of flavor, aroma and body.

Learn to recognize the distilleries. They each have a NOM number supplied by the government, listed on the label. Many distilleries make more than one brand, some have a dozen or more under the same NOM but competing for space on the same shelf! Some of these products are otherwise identically labelled outside of brand information - the same type, percentage of agave, etc. Knowing who is making the product can help determine its quality.

The alcohol content after distillation usually reaches 110-120 proof, so most distillers add de-mineralized water to lower the alcohol content to around 80 proof (40 per cent). A very few companies, like Tequila Tapatio (El Tesoro), stop the distillation when the level reaches 80 proof, so their product is not diluted at all. This gives it more body and a silky texture.

Slow distillation (alquitara) is another traditional, premium process. Handmade tequilas using the old practices are usually the most expensive, but also among the best tasting - like El Tesoro añejo, a fabrica (Tequila Tapatio) that doesn't even have electricity to operate its equipment!

The length of aging in the barrel also affects the tequila - many distillers only age their tequila in barrels for the required 60 days (reposado) or for at least one year (añejo), and may rack it into stainless steel tanks after that to prevent further impression from the wood. Some aficionados feel too much wood can overpower the delicate agave flavour.

Tequila experts also demand that the drink produce a 'pearl' (perla or concha - conch) - a bubble that remains on the surface of the liquid. The bottle is often shaken to see it the bubble appears, or sometimes the tequila is stirred when served. Sometimes a string of bubbles appear around the rim of the glass when tequila is poured. If the perla doesn't appear, the drink is called "tequila cortado" or cut tequila, a term meaning mixto - less than 100 per cent agave.

Cuervo's mass-produced mixto Gold tequila, despite not being 100% agave and having additives like colouring, is the world's best-selling tequila. Cuervo also makes some excellent 100% agave, reposado and añejo tequilas - and a legendary Reserva de Familia añejo that is by all reports the ultimate in smoothness. This year they introduced a $1,000-a-bottle 1800 Coleccion. As drinkers become better educated, the 100% agave tequila's continue to gain market share, even theough mixto tequila remains the best-selling type.

Why the change from frat drink to hip sip? In part it's because the continued prosperity of the North American and European markets allows consumers more time and money to indulge themselves. Premium drinks appeal to the boomers with high disposable income. It's also partly because the boomer culture generally eyes foreign goods and international products with delight and acceptance, rather than the suspicion and xenophobia of previous generations. Tequila is exotic, and mysterious - and has not yet achieved the common-place acceptance of most other spirits.

Both Cuervo and Sauza - the two largest producers, respectively - are changing to meet the increased demand for 100% agave tequilas. For a while, Sauza offered Hornitos as its only 100% agave product. Recently it added a 100% agave version of its premium Tres Generaciones and other brands. Cuervo has two 100% tequilas as well: its Tradicional and Reserva de la Familia and in the last few years made its 1800 brand a 100% agave product. Sauza has also introduced its limited-edition 100% agave Galardon, with numbered bottles.

Premium tequilas are expensive, even in Mexico, and production can be so limited they are not exported. However, many good brands are available for $15-$40 US, including the handmade Tapatio brands like El Tesoro. There are numerous bargains in 100% agave brands, too - Tres Mujeres at about $10 US. This is the result of a new and growing market for tequila, especially in the USA, where it's gaining the same sort of popularity single-malt scotches got a few years back. In fact, figures showed tequila sales in the USA grew 1,500% between 1975 and 1995.

Small tequila distilleries are being positioned in the same vertical market for discriminating buyers for whom expense is no object and quality is their prime concern. However well this may bode for the local economy, it's difficult to tell what impact increased demand will have on quality and traditional production methods in the future.

Reposados are more popular and outsell the añejos, but not just for price. To many drinkers, they offer a better flavor - spicy, peppery, herbaceous, yet mellowed from their resting time in the oak. Several distilleries are now offering premium reposados at similarly high prices as their añejos. Many drinkers, however, prefer the blanco as the "real" tequila for its stronger agave flavours and more robust aromas.

Tequilas vary in taste considerably. There is a very real difference between, say, the reposados of Hussong's - very strong agave flavour - and El Tesoro - solid body and mellow aromas - and Hornitos - peppery bite and long finish - and Herradura - mellow, back-of-the-palate smoothness. You will have to sample many brands before you find the one(s) that suit you best. Despite the confusion of brands and the changing industry, it's worth the effort to discover the real 100% agave tequila, if you're not already familiar with it.

How to drink tequila

The traditional way is to use a tall, narrow shot glass called a caballito. The caballito, with its narrow base and wider mouth, is said to be modelled after the original bull's horn, from which tequila was drunk. The bottom was cut flat so it could rest on a table. It's a perfect size and shape.

Sip it, without the lime and the salt. Forget the margarita mix. Don't even add ice. If you want to taste it, drink it neat - slowly and gently, to enjoy the aroma, the body and taste.. Some people like it served cold, especially the blanco variety. But try it at room temperature if you want to appreciate the full bouquet and body. Taste it as you would fine wine.

Remember that when you open a bottle of tequila, you subject its contents to oxidization, just as you would a bottle of wine. This can rob the tequila of its agave flavours in a matter of a few weeks to a month. Also, you can lose alcohol to evaporation. Tequila doesn't last indefinitely. You have to drink it soon - usually within 1-2 months - otherwise it starts to lose its zest.

Taste and type: subjective approaches

What makes a good tequila? For some it is the earthy, vegetable taste and aroma of the agave. For others it is the sharp bite of the blanco or reposados. Still others prefer the smooth, oaky body of the añejos.

There is no single 'best' tequila - although by all reports the ultra-premium añejos are just about everyone's favourite choice. One of the more visible trends is towards premium tequilas at premium prices. At the top end of the scale are companies like Chinaco, Don Julio, Casa Noble, Patron and Porfidio - the latter topping $100 US a bottle in Mexico (single-shot sample bottles sell for $14-$15 US!). Note that the latter do not at present actually make tequila: they buy what they consider the best from other companies and put their own label on it. More expensive are Cuervo's Reserva de la Familia and Herradura's Seleccion Suprema, both of which sell for more than $200 US in Mexico. Finally, Porfidio's single-barrel Barrique is sells for $500 US ($375 US in Mexico)!

The best advice is to try several brands and several types to find the taste you like. Some distilleries have reputations for making mild, spicy or earthy brands, others for strong alcohol finish or other tastes. Read books to find out what styles the authors suggest for specific brands, and look for those styles that might suit you - and go try them. A good way to introduce yourself to tequila is to find a bar which specializes in it, and a bartender who understands the differences between them, or attend a tequila tasting.

Official designations: The four types of tequila

Blanco or plata (white or silver) is type 1: The most common type, it's considered 'unaged' and is under 60 days old, and may be bottled fresh from distillation. Sometimes this is a harsh, young drink, but it can also be tastier and more robust than highly refined varieties, if it's marked "100 per cent agave". Some distillers may 'rest' blanco tequilas in oak barrels for more smoothness - the maximum allowable period is 30 days.

Joven abocado (young and smoothed, also called gold - oro) is Type 2: basically the same as blanco, but with coloring and flavoring ingredients added to make it look aged. These are also called suave or oro (gold) because of its coloring (usually through added caramel and sometimes oak essence.) In the industry they're known as mixto, or mixed blends. Generally they're not as good as 100% agave, but they are also very popular for export sales. Note that Herradura calls its 100% agave reposado tequila "gold," but it is not to be confused with a gold mixto.

Reposado, Type 3, means rested. This is aged from two months to up to a year in oak casks or barrels. This is where the better tequilas start and the tastes become richer and more complex. The longer the aging, the darker the colour and the more the wood affects the flavour. Reposado accounts for more than 60% of all tequila sales in Mexico. It was the first type of aged tequila.

Añejo (aged, or vintage) is Type 4: aged in government-sealed barrels of no more than 350 liters, for a minimum of a year. They may be aged longer - as long as eight to ten years, although many authorities say tequila is at its best at four or five years. It is usually removed from the barrels and racked into stainless steel tanks after four years because evaporation in the barrels reaches 50% or more. Many of the añejos become quite dark and the influence of the wood is more pronounced than in the reposado variety.

Types aside, all tequilas have similar alcohol contents - roughly the same percentage as any standard scotch, vodka, gin or bourbon - around 38-40 per cent (76-80 proof).

Premium brands: 100 per cent agave

The most important identifier on the label is "100% agave" or "100% agave azul" - cien por ciento de agave azul. This means it is made only from the blue agave plant, and was approved by a government inspector to ensure purity. If it doesn't say this, it legally can be mixed up to 49 per cent with other ingredients. All those non-agave ingredients are the recipe for a hangover. And "100% agave" can make even a blanco tequila into a respectable drink, with a peppery flavor-sharp tang. in general, 100 per cent agave means better quality, flavor, taste and purity. Without it, cane sugars are used in the fermentation process to produce much of the alcohol - but none of the taste.

It's nothing without NOM

NOM on the label means Normas Oficial Mexicana, usually referred to simply as the NORMAS: it means the tequila meets government standards - but it's not any guarantee of quality. Without the NOM stamp of legitimacy, you can't even be sure it's tequila in the bottle. All 100% agave tequilas must have a NOM identifier on the bottle.

The number after NOM is the distillery number, assigned by the government. Look closely and you'll see a lot of apparently competing brands with the same NOM number. That's because they're all produced at the same distillery, regardless of any real or invented history or legend behind them. In fact, there are only about 70 licensed tequila distilleries in all of Mexico - and they make more than 500 different brands. Only one of these companies does not have a license to make 100% agave tequilas.

NOM does not indicate the location of the distillery, merely the parent company. The location may also be listed on the label, but it may also be the address of the parent firm, not the actual fabrica. However, some brands like Porfidio and Patron do not have a distillery, but instead purchase what they consider the best tequila from other manufacturers and put their own labels on the bottles.

Some tequilas are bottled outside Mexico using bulk Mexican mixto tequila as a base. These are not governed by the strict Mexican laws and can be adulterated with other non-agave, non-tequila ingredients by the bottler. There is no guarantee as to their quality or even the amount of tequila they contain. These will never be 100% agave.

Labels - hidden clues and directions

Learn to read the label so you at least know what you are buying. There are many legal requirements for information to be displayed on a tequila label but none of them necessarily mean the contents live up to anything more than minimum standards. There are ten elements you should be able to recognize on any tequila bottle label:

• the type (tipo) of tequila (blanco, añejo, reposado, etc.)
• the purity (only 100% agave is labelled as such and if it doesn't say it is 100% agave on the label then it is a mixto). Note that since the shortage in 1999-2000, several companies have changed their 100% agave products into mixto to keep prices low
• the NOM (distiller registration number). Take a NOM list with you - there are more than 500 brands produced by about 70 distillers. The brand (name) is not any real indication of who makes the product, so a good NOM list is an absolute necessity to know who the players are
• the distiller's name and address (not always shown in full on the front and sometimes only indicating a town and state). This may be the parent company's address, or the administration office
• CRT - indication the Tequila Regulatory Council has certified the product - not a guarantee of quality, however - simply that the CRT has approved the process at the company's site
• Hecho en Mexico - Made in Mexico. 100% agave tequilas can only be made and bottled in Mexico. Hecho a mano means 'handmade' and is not an official term but usually indicates traditional production processes
• DOT - denomination or origin number, indicating compliance with Mexican regulations regarding where the product was made. Not on all labels. The brand name. Usually accompanied by a graphic or a logo. This doesn't indicate who makes the product (see NOM).
• The alcohol content. Tequilas in Mexico are usually 38-40% alcohol, but legally may be higher, up to 50%.
• Of course it should also say "tequila" on the label - otherwise it could be anything inside the bottle.