Every grocery store carries a wide variety of fresh, canned and frozen berries. Look for ripe, colorful and firm berries with no sign of mold or mushy spots. Berries can also be found in the frozen section of the grocery store. Once they thaw, they will not be as firm as freshly picked berries, but they are still delicious and good for you.
For the freshest berries, try farmers' markets that offer berries harvested that same day. Some berry farms allow you to pick your own berries.