If they find something out of the ordinary, that information could give them a jump on the field. If they catch a fish in practice, some pros will even cut it open to see what it's been eating. While most anglers use their sonar devices to locate the fish they hope to catch, guides and tournament fishermen are always on the lookout for schools of forage fish. Where there's a concentration of baitfish, the predators won't be far behind, and every pro knows it. They'll also keep their eyes open for flocks of feeding gulls, insects floating on the water and baitfish swirling the surface.
Big fish eat small fish, small fish eat tiny fish and tiny fish eat insects and plankton.
Wave action stacks plankton next to shore. That plankton attracts minnows that attract small fish, which sets the entire food chain in motion. Brush piles and weeds are well-known fish magnets. One of the big reasons is that baitfish seek shelter in cover. Deadfalls, fish cribs, boulders, stumps or anything else that provides a hiding place for bait should be checked.