Place watermelon in road, in path of approaching car. Before the car can run over it, wave to the driver and make him stop. When he gets out to pick up the watermelon, go in his other door and steal his address book. Find out where he lives. Later that night, go to his house and look through his windows until you see the watermelon. When he is asleep, sneak in and steal the watermelon. Put the watermelon in the driveway, behind his car. Wait until morning. When he backs over the watermelon, if the shell is squished, the watermelon was not ripe. If it shatters into many pieces, it was ripe.