Since avocados often are one of the pricier items in the produce aisle, learning how to choose the good from the bad makes economical and culinary sense. Most stores won't approve of customers slicing open the avocados to determine their ripeness, so telling when an avocado is past is prime comes down to a matter of touch and practice. Once at home, checking the condition of an avocado that has been sitting for a few days becomes more straightforward.
Pick up an avocado and gently squeeze it. When an avocado has gone bad it feels mushy and might even have sections that feel as if nothing is inside. This means the inner fruit has spoiled and is starting to rot.
Look for avocados that have broken or dark, soft spots on the skin. If these avocados have not already turned bad, they're on their way out and not worthy of purchase.
Slice the avocado open. At home, check the freshness of an avocado by opening it and looking inside. A bad avocado has dark brown and black spots, generally starting from the stem portion of the fruit. If these are isolated in one or two spots, cut the bad portion away, and check the rest of the avocado to see if it's salvageable.
Taste an avocado that has one or two dark spots but otherwise looks fine. Avocados just on the edge of turning might still have a creamy green color but will taste slightly "off." A good avocado has a clean, smooth taste with a slightly sweet aroma. A bad avocado will not, often exuding a somewhat musky odor and flavor.