How to Ripen An Avocado
The most effective way to ripen an avocado is to place it in a paper bag with an apple or a banana.
What you will need
1 Apple or Banana(Nutritional facts 102 calories, 6.94 g fat, 11.33 g carbohydrates, 1.07 g protein, undefined mg cholesterol, 3 mg sodium)
How to cook
This avocado is bright green and very firm. Some varietals are firm and green when ripe, but that's not the case here. This avocado is way too ripe to be any good.
Or apples will work as well. In fact, most any fruit will work, including: tomatoes, kiwis, apricots, peaches, honeydew and many more.
Bananas produce a plant hormone called ethylene that can induce ripening. By sealing them with an avocado in a paper bag, you will still allow the fruit to breathe, but the concentration of ethylene will be increased, causing the avocado to ripen more rapidly.
It still may take several days for the avocado to be ready to eat. And keep in mind that whatever fruit you put in the bag may ripen more rapidly as well.
Still, this is the most effective way to hasten ripening, and the only functional option. I've seen some articles suggest putting an avocado in the oven or a microwave to ripen it up. Neither will work. They might help soften the flesh a little, but you still end up with an unripe avocado.