The FIRST step is to determine the source of the problem - more specifically than "it's the hub." The hub should be disassembled and the cups/cones inspected for pitting, etc - then replace cones if pitted. If all is well then repack with new balls and good waterproof grease. Note that if there is very little grease or it's too thin the balls can make noise as they click against each other. You should also check the spokes at the crossing to see if they have developed burrs, which will also click at sometimes unpredictable times.