The Margarita, as its name implies, was probably invented for a woman. Until it came along, only men (and a few hardy women) enjoyed Tequila, the liquor made from the agave plant.
Today, thanks to efforts by José Cuervo and others to expand the appeal of the Margarita to wider audiences (and younger ages), the Margarita bears little resemblance to the original, especially in California (and Florida), where the trend appears to be to find larger glasses, slushier textures, and newer colors with different fruits, until they are indistinguishable from a 7-11 Slurpee. It's now almost impossible to find a good Margarita in California (or for that matter anywhere west of El Paso, Texas). Even the establishments in the Mexican border towns seem to have forgotten how to make them.
One reason is the loss of bartending as an art. You won't find well-trained bartenders in most bars any more. Why hire one, if all you need is a basic inventory of processed mixers in plastic jugs, some booze, a blender, and a large supply of ice and sodas? And since the clientele are getting younger and more female, who demand a drink that tastes similar to the sweet sodas they grew up with but can still give them a buzz, excellence is no longer economical. Most bars now concentrate on the highly-profitable happy hour drinks -- sweet, slushy, and ice-cold, designed to be gulped rather than sipped. Good luck finding one that serves a real Margarita.
So now we hear debates about whether Margaritas should be served "frozen" or "on the rocks," when the answer is neither. Also, whether to use Rose's Lime Juice or Sweet & Sour (again, neither).
Margarita is simply half tequila, one third fresh lime juice and one sixth triple sec (citrus liqueur). So a single 5-oz Margarita will contain 2½ oz tequila, 1½ oz lime juice, and 1 oz citrus liqueur (usually a quality triple sec such as Cointreau). The rim of the glass is rubbed with lime juice and dipped in salt. The ingredients are shaken with cracked ice and strained into the salt-rimmed glass. It's served garnished with a wedge (not a slice) of limón verde (Mexican lime).
The Margarita recipe calls for slightly more lime juice and less liqueur than the classic "Sour" or "Sidecar" recipe (which is simply 2 parts liquor, one part lime juice and one part liqueur). This makes it more refreshing than the Sidecar. And if you want an even more refreshing and less potent variation, try the Margarita Squirt.
As can be seen, the original Margarita is smaller and more potent than today's huge, frothy happy hour concoctions. But the best time to enjoy a Margarita is not at a noisy bar, but in a quiet cantina or at home with a few friends, preferably on a sunny patio. Margaritas enhance conversation, so to maintain the proper boundary between conviviality and inebriation, they should be sipped very slowly. And they should always be served with food, even if just a bowl of tortilla chips and salsa fresca.
Happy hour Margaritas are almost always made with a too-sweet, artificially-flavored triple sec, or even a citrus-flavored syrup, instead of the more expensive Cointreau, and Sweet&Sour mix (or limeade) instead of the fresh lime juice. If you're going to take these shortcuts, you might as well use a cheap tequila as well and invite your frat buddies. Rose's Lime Juice is the best substitute for fresh limes (and is made from real Mexican limes). You pay for the convenience, though.
The citrus liqueur is important because its sweetness balances the tartness of the lime juice and enhances the citrus flavor while complementing the agave flavor of the tequila. The best (and most expensive) choice is Cointreau, but any good-quality triple sec or citrus liqueur may be used, such as Curaçao (made from orange skins) and Limoncello (an Italian lemon liqueur). If you're in Mexico, pick up a bottle of Controy, a Mexican orange triple sec that Mexican bartenders use (and costs about a third of Cointreau). Some Margarita aficionados use Grand Marnier, but only in place of half the triple sec. Another good substitute for half the triple sec is Damiana, a herbal liqueur and reputed aphrodisiac native to the Baja peninsula.