Choose onions that are firm and dry with bright, smooth outer skins. The neck should be tightly closed and the outer skin should have a crackly feel and shiny appearance. Onions should smell mild, even if their flavor is not. Avoid selecting onions with dark patches or sprouts.

Store whole onions in a cool, dark, well ventilated place for use within 4 weeks. Because onions absorb moisture, do not store them below the sink. Refrigerate cut onions in a tightly sealed container for use within 2-3 days.