Easy Margaritas:

Tequila
Splash of Cointreau
Margarita Mix
Lime Juice (be liberal)

Pour over ice and serve! Proportions are to taste. I normally use about 1.5 shots of Jose Cuervo, about a 1/4 shot of Cointreau, 6 oz. Margarita mix, and 1/4 to 1/2 a lime's worth of juice.