The best golf swing trainers reinforce muscle memory through repetition. Look for a system that builds a familiarity with basic principles. Once you have mastered the basics, you can work on perfecting your swing and increasing your power.
Opt for one of the swing systems that delivers a 'click' if your release is executed with perfect timing. The fact that you don't need an instructor to tell you if you are on track is a huge bonus. It is also useful if a demonstration dvd or video is included. This will motivate you to make the most of the golf swing trainer.