duuuude, I must respectfully disagree on the tequila point. I have done exhaustive side-by-side testing of numerous margarita variations (all in the name of science). My finding was that using a 100% agave tequila (not a high end one, just 100% agave) makes it an entirely different and vastly better drink than using corn syrup-y and chemical-tasting rotgut like Cuervo Gold.
As another marg tip, use fresh squeezed lime juice… much much better than any mix on earth.
My recipe (sorry for the fraction):
3 parts fresh squeezed lime juice
3 parts 100% agave tequila
1 part triple sec
3/4 part sugar
