Easy Recipe-
5 parts Lime mix
5 parts tequila
3 parts triple sec
Lately I've been buying this Cuervo Oranjo, and cut back my lime mix to 4 parts.
The key to the above recipeis finding some really great lime mix. My favorite is Collins Bar Lime, though I haven't seen it in forever, I don't know if they make it anymore. The lime mix should be more sour than sweet. Once thing I definitely don't like is a margarita with too much sugar.
For strawberry margaritas, thaw some frozen strawberris (the kind in sugar), and simply puree equal parts tequila and strawberries. That's your mix. When you're ready to serve, simply combine with ice in a blender.