Unlike most familiar fruits and vegetables, avocados do not ripen on the tree. Instead, they fall off (or are harvested) while they are still hard and unripe. The avocados then ripen over the next five to 10 days until they reach their peak ripeness. A perfectly ripe avocado will be firm but give slightly when you squeeze it gently. A hard avocado with no give is unripe, and a soft or squishy avocado is overripe. If you are not ready to use your avocados when they reach peak ripeness, you must store them properly to avoid having them become overripe.
Things You'll Need
Place your avocados in a plastic (not paper) bag if you wish to bag them. Ideally they should not be in a bag at all, but if you must use one, avoid paper. Putting avocados in a paper bag will speed their ripening process.
Put your avocados into one of the warmer parts of your refrigerator. Some refrigerators get cold to the point of freezing in some areas, such as against the sides or the back wall. Do not put your avocados into these areas–freezing an avocado or storing it at too low a temperature can destroy its creamy texture.
Store your ripe avocados for 2 to 5 days in the refrigerator. Check them daily by squeezing them gently to see if they are becoming overripe. Remove any avocados that are beginning to become overripe and use them immediately.
References and ResourcesFood.com: Avocado
California Avocado Commission: How to Choose and Use
What's Cooking America: Avocados