You want a nice creamy bottom - not much cream, it didn't sit and ripen on the vine long enough. Too yellow, it sat too long. Look at the stem end - you want the remaining stem peice to be brown & dry, not green & moist - when a watermelon ripens naturally on the vine, like in your home garden, it's just right when the stem starts turning brown & dying. A moist green stem means it was picked too early. Thumping isn't terribly reliable, because an over-ripe watermelon will be hollow too - and you don't want one that's starting to rot on the inside. Go with appearance.
at 12:47 PM on May. 27, 2011