I watched a golf channel academy where these three elements were explained to create more consistency in one's golf game.
The Set up should be the same every time. Make sure the hands fall down freely, approximately over the toes. When you realize you are too far in one direction, instead of just moving your feet, move your whole body as if you were rotating around an imaginary circle, where the ball was in the center. Make sure when you set up and bring your right hand onto the club that your shoulders are still parallel to the target. The tendency is for the right shoulder to then be in front of the left.
Rhythm should be consistent. The club should hit the ball when the weight is shifted onto the left foot. Try hitting the ball at 50% until you get the right timing. Then move up to 70% while keeping the same relative rhythm. If that doesn't work, move back to 50%.
A drill you can do for this is line up four balls on the tee. Hit the first with good rhythm...the ball should fly straight. Hit the next one where your hips and weight rotate first and the hands are late. The ball should go right. Next, hit one ball where the hands come through first...the ball will go left. Lastly, hit a ball with perfect rhythm and timing and watch it fly straight as an arrow.
The pre-shot should be basically, assess the surroundings, envision the shot your are going to take, select your club, practice the swing feel, and then execute the swing feel. During the swing, just try to recreate the same swing feel you had during your practice swing.