Trick to keeping guacamole from turning brown
Guacamole seems to go brown with exposure to air, as does avocado. While it will not solve the issue entirely, covering with cling wrap directly on the surface helps maintain color for an extended period. Rather than pulling the wrap tight across the top of a bowl / container, place the wrap directly on top of the guacamole. Use your hand to smooth out the top so that no air is between the cling wrap and guacamole. This requires a bit extra cling wrap, as you need to get it up the insides of your bowl, but it makes a significant difference.