Watermelon lovers know that it's never a good idea to buy a watermelon out of season because they're tasteless. But when summer rolls around it's the perfect time to get your hands on a good watermelon. You know you're picking a good melon if it's fairly symmetrical, whether it's round or oval. If the rind has bruises, cuts, or dents you shouldn't buy it. Another good way to tell how ripe a melon is is by picking it up.