My favorite plastic jig is the Case Trout worm, and by working with that one, developing the technique across the board, I've found that any plastic with a pointy tail, suspended under a float, works FAR better if tied so that the tail of the jig is pointing upward, rather than horizontal.
Usually, all this takes is a good knot, and then pulling on it until the tail of the jig points up, where it typically stays well until I catch a fish, when I have to return it to position.
It seems crazy, but it really makes a difference.