It's really nice to use fresh fruit for things. I was never a big fan of pre-made lime juice or lemon juice as they taste really watered down and they just don't add the flavor and the bite you need to turn up your cocktail. This is a good way to make your own sweet and sour mix.
Basically, all you add is simple syrup (1 cup water, 1 cup sugar)
1 part lemon juice
1 part lime juice
shake it up
There you go!
This is a real sleeper for cocktails as the pre-made stuff is way too sugary or way too bitter to really add anything to your taste buds. Check it out and enjoy!