Instructions
Make sure you own one of the three games mentioned in the introduction. Without them, you will be doing nothing more than moving your hands imagining the game, and you don't need a Wii for that.
Forget that it is a game and take the proper setup position as in a real golf game. That means your legs should be parallel to the target line and slightly open, to give you the necessary steadiness.
Give full power to your long shots by swinging the Wii controller high, reaching the back of your right shoulder (the opposite applies to left-handed players). Make sure you have the controller's strap firmly attached to your wrist to avoid domestic accidents during play.
Practice your footwork. With the exception of "My Personal Golf Trainer" the position of your feet is not very important to your shot when you're playing on the Wii, but serious golfers know that without the twist of the leg, you cannot increase your swing speed. Nonetheless, if you try to hit the ball hard, having your feet buried to the ground may result in serious back injuries.
Be persistent with your practice. Nobody became an expert in one day and even though video games cannot truly resemble real life, use your on-screen results to measure your progress and correct your mistakes. Don't forget to regularly practice your swing using real golf clubs, as in the end of the day, that's why you started seriously playing golf on Wii.