A vertical approach would be best. That can be accomplished by either sitting over them in a boat or using a slip bobber. I prefer the boat and no bobber myself. A lot of the time Winter crappie don't want the bait moving at all. Just lightly twitch ever so often and let sit. You can also raise the bait up a couple of feet and let it fall. Be sure to watch your line incase they hit it on the fall.
Good luck.