Cantaloupe:  The outside should be tan/golden in color with a light green lines and a little firm. Watermelon:  Should be nice and heavy. This indicates it is full of water. It should sound hollow when tapped with your knuckles. Honeydew: The outside should smell fragrant, sweet and pale/light lemon in color. It should feel firm, but give slightly when pressed on the end where it the stem was.