Talk outlines should be extremely concise and visually uncluttered. 12-15 lines of text per transparency is plenty. Remember to only show us the visual aid until you are ready to use it hide it until then and put it away after you are done. No obscene visual aids or distracting ones should be used. It's easier to keep focused on someone who's moving than on a motionless talking head.
Hand gestures are also good.
It's possible to overuse these devices, of course. Simply crossing from one side of the room to the other every three or four minutes is probably enough. Monotones are sleep-inducing. Since it's possible to speak in a lively, animated manner without changing pitch, many people don't realize they have this problem. Get a trusted friend or colleague to listen to your delivery and give you honest feedback.