Not sure what melon to pick? According to Woman's Day, here are some guidelines!
Cantaloupe: Look for an indented stem end. This means the melon came off the vine at the proper time, not too early.
Honeydew: Look for a smooth rind that is white, yellow, or light green. A ripe honeydew should have a slightly fruity aroma and be soft at the stem end.
Watermelon: If it sounds hollow when you give it a good thump, it's ripe! Look for a firm, nicely shaped melon that has a creamy yellow underside where the melon has lain on the ground long enough to ripen.