Ensure avocados are optimally ripe by looking at the skin and applying firm, yet gentle pressure with your palm, while avoiding the use of the fingertips. Avocados are ripe when the skin has a uniform black color and the flesh yields to the pressure. If the skins are green or the flesh remains firm, they should be ready in four to five days. If the skin has dark spots and depressions or the flesh is mushy, they are overripe.
When buying an avocado, consider when you plan to use it, for optimal ripeness. If using it the same day, you want fruit that has already reached its peak. However, if your plans are for use in a couple of days, choose the dark yet firm fruit that is just starting to change color. If your plans are for using the fruit four to five days in the future, choose a bright green, firm avocado that is free of blemishes. For use beyond five days, the best option is returning to the store at a later date.
If you cut an avocado and find it is not yet ripe, sprinkle both halves with lemon juice, and wrap it with plastic wrap. Check it periodically, and use it when the flesh is soft. If avocados are ripe but you are not yet ready to use them, puree the flesh along with 1 tablespoon of lemon juice per avocado in a food processor, and freeze the puree. Use the avocado puree within four to five months as a spread on sandwiches, for making dips or in dressings.