Any lure that imitates the minnows near the docks will do the job. The most efficient crappie lure is a jig tipped with a small curly tail jig colored red or yellow. If you use lures, cast as close to the dock as possible into the shady side of the dock. Your retrieve will normally be straight, slow paced through the water back to the boat. As you retrieve, try twitching the tip of your pole to give the lure a different action.
Some anglers add the lure under a bobber.
Under a float just cast, let the lure settle and then twitch the tip of your pole, but don't retrieve immediately. Twitch, giving the lure some action, stop, twitch again, stop, then twitch a third time and retrieve very slowly. Half way back you can stop reeling and twitch again. Also, you can tip your jig with a live minnow. Hook the minnow through both lips.