number one is FORWARD! get him more forward without any regard for how he deals with the bit or where he holds his head, or whatever. Work first on the straightaway of the arena, just giving him the rein and getting him to bust out and go. Warmbloods can be like that. But once you get the engine revved, then you'll have something to work with when you go to shape it, which will be part of the excersizes done to build the balance of the horse.
When things start to grind down, bring up the energy and get the horse FORWARD!