Most recipes call for lemon or lime juice. The acidity in that keeps them from turning brown much like lemon juice over apples keeps them from turning brown as quickly as well. It just slows the rate of oxidation.
Hope that helps. I've made guacamole before as well as salsa and pico de gallo and it's not terribly difficult. there are a lot of good "starter" recipes out there that you can adjust to your own tastes. (Some people like tomatoes in their guac, some dont, etc)
I'm going to be making some tonight for Cinco De Mayo!!
edit: I JUST remembered... in Kindergarten we once had to bring in a food beginning with A. My mother convinced me everyone else would bring apples, so she forced me to bring an avocado. I remember everyone saying how weird and disgusting it was. I wanted to hide. Hehe.. thought it was an amusing story