If you are making a dish with avocado, you'll find that avocado begins to turn an unpleasant shade of brown once it is cut and exposed to air. One easy way to keep this from happening is to sprinkle the avocado with the juice of a lime, lemon, or orange. If the avocado is in a salad or other dish, sprinkle the whole dish with the juice. If you have used your avocado to make guacamole, in addition to the juice, putting the pit of the avocado in with the guacamole helps keep the surface from turning brown.