You always hear that putting lime juice or lemon juice on avocado will keep it from turning. Try this and you'll be surprised at the results!! Buy just one avocado, cut it in half. You can leave the pit in one half if you like, it won't make a difference. Now, put a little lime or lemon juice on just one half. Put absolutely nothing on the other half. Remember which half is which. Place each half in a zip loc bag and put in the refrigerator. Check your avocado halves in a couple of hours, then check again a few hours later, or even the next day. The half with the juice turned way darker than the half with nothing on it!!!! For keeping guacamole as green as you can, place some type of saran wrap right on top of it so there is no air between the guacamole and the wrap. Then put the cover on the container.