9dreizig's lady got me drinking Cadillac Margaritas this summer...
The official listing is
1.5oz Gold Tequila
1 oz Grand Marinier
1/4oz fresh lime juice
However I always just eyeball it, with the tequila part getting stronger the more I drink..
So around 2 parts Tekillya, 1 part GM, and top off with Crystal Light Margarita mix. Nice light marg with a smoother citrus tone.