Pick the perfect
Look for a yellow field spot. This usually means it was on the vine longer and is full of flavor.
Dull & Dark
Look for dark & dull melons which is a sign that the melon is ripe.
Lots of Webbing
Webbing or sugar spots means that the melon is seeping out sugar and is a sign of sweet melon.
Round & Heavy
Find a watermelon that is a uniform size (oval or round) and heavy.