Pick out a melon that is gold in color.
Smell the melon. A sweet scent indicates the melon is ripe.
The melon should be firm and free of soft spots.
Shake the melon. The seeds should be rattling around a little inside.
Knock on the melon a little with your fist. A deep sound indicates a healthy melon that will be sweet and tasty. Avoid melons that produce a hollow sound.
Hope this helps!