Here are some key points to keep in mind to pick a ripe, juicy, and sweet watermelon. Choose a watermelon that is symmetrical and uniform in shape without bumps or cuts and heavy for its size. It should have a firm rind that doesn’t give to pressure or scratch easily. Check for the yellow spot: Watermelons develop a spot where they rest on the ground. A creamy yellow spot indicates it's ripe Last but not least, tap the watermelon and check the sound. A ripe one will have a deep sound, while under-ripe or over-ripe melons will sound dull or hollow.