Stone fruits such as peaches, nectarines and plums do not continue to ripen after they're picked, but they do soften. If you must tug forcefully on a fruit to pull it from the twig, it's not ripe. When you purchase peaches, nectarines and plums from the store, you don't have the luxury of waiting until they fall easily from the tree. If you purchase hard specimens, soften them at home to improve their texture.
Paper Bag Method
Ripe nectarines, plums and peaches give a little when you press against their skins. If you've purchased hard fruit, place them in a brown paper bag with a banana or apple and fold the top closed. The fruit produces a compound called ethylene that enhances the softening process. Check on the fruit's progress daily as it can turn from soft to mushy quickly. Once you're satisfied with the fruit, store it in the refrigerator for up to a week.