Here’s what to look for. Essentially, you want the most juice possible (detectable by its heft and the slosh when you shake it), and you want to make sure that the shell is intact. Look for damp spots on the outside of the shell that might indicate small cracks or openings, and make sure that the “soft eye” is in good condition, as this is a common entry point for infection or insects. Fresher coconuts are rich brown; older ones are grayish.