Try this;
Whichever body of water you select, focus on a likely cove or channel, then treat it like a small body of water, similar to a pond. Don't worry about where else they might be and just try to figure out where they are in the limited area you're in. Once you establish the correct pattern/ depth and start catching some crappie consistently, seek similar depth and cover in other parts of the lake to see if the pattern holds. The crappie are feeling the days getting shorter and the water cooling down, so they're going to concentrate on baitfish, so check out the channels and flats beside the channels where water enters the bigger body of water. If nothing cooperates, move to the next deeper break line or dropoff until you locate the fish. It works for me, I hope it works for you. Good fishing.
Jim