The best bananas to use for baking have skins turning brown with black spots, and they are soft to the touch. Overripe bananas can be put in the freezer, unpeeled, for later use. When you're ready to use them, just thaw them, cut off the top of the peel, and squeeze the banana into your measuring cup.
Make sure to use a light touch when combining wet and dry ingredients. Stir just until moistened. Don’t worry about small lumps; they will disappear during baking. Overmixing will result in a dense, tough quick bread.