COMPARE DOM PERIGNON to Jose Cuervo and many a champagne drinker will blow fizzy wine through the nose in terror. Yet in 1758, 42 years after the death of Dom Perignon (the blind monk purported to be the "father of champagne"), Jose Antonio Cuervo became the first man licensed by the king of Spain to produce mezcal wine. Today the production of tequila is more highly regulated than that of almost any other alcoholic beverage in the world. Like champagne and cognac, only spirits produced from very particular ingredients, processes, and regions can legally be called tequila. As there is Champagne, France, so there is Tequila, Mexico.

Tequila's origins date back to pulque, a milky, beerlike beverage ritually consumed by Aztec priests. In a rough sense, the end product of pulque production is the first step in tequila production: fermentation of the liquid extracted from the heart of the agave plant. Later, conquistadors entered the region and, favoring something a bit stronger to help them relax after laying waste to an ancient culture, they applied their distillation techniques to pulque, producing a potent brew called mezcal. Continuing refinement in the process eventually yielded what we call tequila.

There are two categories of tequila, 100 percent agave and mixto. Though mixto must contain at least 51 percent blue agave, nowadays there's no reason not to opt for the pure stuff. The four types are blanco or plata ("silver"), joven abocado, reposado, and añejo. Blanco is not aged beyond 30 days and is the raw, colorless result of the distillation process cut with water to make it 80 proof. Joven abocado, or "young and smoothed," is up to two months old. Also known as "gold" because of the coloring and flavorings added to make it appear more aged, it's the best-selling variety in America (think Cuervo Gold). Reposado, or "rested," is when things start to get interesting. Aged from two months to a year, repo (as it's also known) is notably smoother than the first two types. Añejo, "aged" or "vintage," is the highest-quality tequila. Kept in government-sealed barrels for no less than a year and often longer, it's usually darker in color and mellower due to the barrels used in its aging.

Salt and lime are for makin' jerky and covering the scent of mass graves. They're also masking agents for bottom-shelf fare. All that's required for premium-tequila tasting is a glass of water (and possibly a cold beer) to cleanse the palate between sips, a stout liver, and no sense of propriety. I hold a quasi-religious affection for the sacramental qualities of tequila, and I'm blessed to live in the same city as Tommy's Mexican Restaurant on Geary Boulevard (5929 Geary; 415-387-4747), home to a reliquary of more than 250 100 percent pure agave products – the largest selection in the United States. Behind the bar you'll find the pope of tequila, Julio Bermejo, preaching to the assembled acolytes.

To begin, we chose two repos: Centinela, aged six months in Jack Daniels barrels, and El Tesoro, aged six to eight months in Jim Beam barrels. Owing to the delicate nature of tequila, it helps the spirit to mature in bourbon barrels, as some of the more pungent flavors imparted by barrel aging have been drawn off in previous use. Served in small, thick glass snifters, the Centinela had slight hints of cinnamon, while the El Tesoro smelled of eucalyptus and tasted of olives.

Our palates primed, we moved up to the Centinela Añejo and El Tesoro Añejo to taste the age difference. Both had a pale green cast and were noticeably smoother, but the El Tesoro Añejo stood out for its pronounced vanilla scent, full-bodied oak taste, and vanilla finish. Maturity definitely makes a difference. Our obvious surprise prompted Bermejo to put two more bottles on the bar. The first was the widely available tequila Chinaco Añejo, in its distinctive bottle. The second was also Chinaco Añejo, but the bottle looked more generic. No flashy colors, no wacky lettering, no sculptured bottle. Pouring a snifter of each without instruction on which to try first, Bermejo sat back to watch our reaction. We tried the fancy bottle first. Subtle black licorice undertones. Nice. Then I raised the second glass, noticing the distinctly darker color. The taste was almost explosive. The whiff of black licorice in the first became a mouthful in the second, and the finish was like a dark chocolate, caramel-centered candy. The difference? Bottled in 1996, prior to the agave shortage plaguing the tequila industry, the second was crafted to higher standards.

In the late 1990s, exploding demand, an agave crop decimated by frost and blight, and the desire to maintain margins resulted in more commercially driven, as opposed to craft-driven, production in some houses. Yet this same crisis has spurred others to value rarity and return to the careful, quality-driven production that has made superlative tequila easier to find.

As always, a pilgrimage to Tommy's illuminated universal truths applicable to any worldly pursuit. This time I was reminded that labels don't mean shit and that an understanding of the conditions and methods of production are essential to making rewarding selections. Negative associations and outright snobbery have kept tequila from claiming the respect it deserves, or maybe the culture that surrounds it is still a little bit too loony. In any case, it just leaves more for us who know a good thing. Ain't no buzz like a tequila buzz