You mentioned that your particular spot has rocks. Crappie like rocks, but especially those that create structure such as a rocky point, big rock pile, or maybe a small group of big boulders. Find out, with sonar or from local fishermen or baitshop, the current depth of the shad or other forage fish. Then I'd fish near the rock structure (or woody cover if any) at that depth by casting or slow trolling. For the bigger crappie, a tube jig of at least 2 or 3 inches, a good-sized baitfish, or small crankbait should work.