Discard mushy, shriveled, or moldy berries. Wash them quickly, but only just before using them. Blueberries are best used immediately, but can be stored (preferably in a single layer) in a moistureproof container in the refrigerator for up to five days. To freeze blueberries, place fresh berries in a single layer on a cookie sheet. Freeze them right from the container; be sure to not wash them before freezing. After they are frozen, transfer to a sealable plastic bag and store. When you are ready to use the blueberries, measure out the ones you want, and then wash them. While there is no harm in refreezing blueberries that have been thawed, their texture will suffer.