People have different opinions about this, based on personal schedules and tradition. Some like to go to the Shore in May, before the summer crowds arrive. Others like to go down right after school lets out in mid-June. Still others wouldn't miss the 4th of July at the Shore. But from a meteorological stand-point, I always recommend... September!
Not only are businesses still open (some, with marked down prices) and beach crowds smaller, the air temperatures are often less brutal than earlier in the summer and the ocean water is often at its WARMEST! Why? Click on the next topic When is the ocean the warmest? to learn more.