Picking the best box of berries is pretty instinctual: you want plump, fragrant berries with a vibrant color. But because berries are stored in such close quarters, one bad apple can spoil the whole bunch in a flash, so it's important to be reasonably thorough: check the box out from underneath or give it a shake to move the berries around. The biggest red flags to be on the look-out for here are signs of mold.