Few things are better than a good margarita. Even fewer things are better than a great margarita. The foundation for any good margarita is in the flavor of a tequila. People constantly argue blanco versus añejo versus reposado). For my particular taste, I've found that I like blanco (silver) or reposado (rested) the best. Your mileage may vary.
However, much care needs to be taken as well to select the appropriate orange liquer. Using French orange liquers (such as Grand Marnier or Cointreau) is seen by some purists as diminishing the "authenticity" of the margarita (and even more forums will debate the true origin of the drink itself). I like the complexity of the Grand Marnier intermingled with the sweetness of the Cointreau. I think any margarita can benefit from a careful mixing of the orange liquers.
Traditional margarita recipes vary, but are usually a 3:2:1 or 3:1:1 of tequila, lime, and orange flavors. For most people, this results in a very strong margarita, which is why so many people get them frozen (yet another line of debate opens as to the "authenticity" of serving this drink frozen).
This recipe doesn't keep the traditional ratios intact. Instead, I use 4:3:2:1 for tequila, orange liquer, lime juice, and lemon liquer, and cut it with 3 parts of water and 2 parts sugar. If Mexican limes are used, you can lighten up on the sugar, since Mexican limes are sweeter than other limes.
Without further ado...
Aaron's Ultimate Margarita
16 oz ice cubes
8 oz silver tequila (100 Años Silver is what I use)
2 oz Grand Marnier orange liqueur
4 oz Cointreau orange liqueur
8 oz simple syrup (I make mine as 1:1 water/sugar)
2 oz water
2 oz Caravella Limoncello
4 oz fresh sqeezed lime juice (preferably from Mexican limes)
Pinch of salt
Combine in a pitcher. Garnish drinks with a lime wedge. This makes about half a pitcher, which is great for company.