Got a hard avocado that's preventing you from taking a one-way trip to guacamole town?
You can speed up the ripening process with some ordinary white flour and a deep bowl or paper bag. Stick your unripe avocado in the bowl or bag, cover completely with flour and let it sit for a day. After 24 hours, that avocado will be guaca-ready. (If it’s a very young avocado, you might have to give it some more time).
This works because the yeast in the flour speeds up the ripening process.