Ralph Ostrowski is the first bail bonds target for Maude, who says that he is hiding out at the quarry. Open up your map and look southeast of Trevor's home in Sandy Shores to find Davis Quartz. He's located at the very center (or bottom) of the quarry and when you get close to him, he will take off in one of the nearby vehicles.
To get the maximum payout, you want to keep the bail jumper alive, so give chase and wait until he's on actual road before trying to shoot out the tires of his vehicle. If that doesn't work, keep smashing into or shooting his vehicle until he eventually stops (make sure not to shoot him), upon which he will surrender. Take him back to Maude's to get your reward.