Have you ever purchased avocados, with plans to use them soon, only to find that they are too firm. Place the avocados in a paper bag with at least one banana. The natural ripening agent, ethylene, which bananas give off, will ripen those avocados in as little as one day.
Not in a big hurry? Simply place your avocados, next to the bananas, on your counter, and they will soften up nicely in a couple of days.