Following the advice of well-meaning amateur tennis coaches could be throwing a monkey wrench into your game. Here are some of their favorite myths. TAKE THE RACKET STRAIGHT BACK: Sounds and looks efficient, but few amateurs or pros actually prepare that way. Most favor the more rhythmical loop or figure-eight backswing. Try imitating the way Wimbledon champ Evonne Goolagong turns and brings the racket back and through in one smooth, uninterrupted motion. ARM STRAIGHT AND RACKET HEAD HIGH: Wrong. A stiff or locked arm makes for a rigid stroke without feel, while a little bend in the elbow acts as a "coil" to give power to your shots. Cocking the racket head high above the wrist results in jerky, erratic drives. For flowing groundstrokes, keep the racket head parallel to the ground at contact. SWING LEVEL: Obey this injunction and you'll be lucky to hit another ball over the net by Christmas. Swinging on the horizontal precludes the high followthrough needed to lift your groundstrokes deep to the opposing baseline. Put your drives into high gear by thinking "low to high" as you swing. WATCH THE BALL TO THE RACKET: Studies have shown that this is virtually impossible to do (and can lead to a kinked neck in the process. The real trick -- as any golfer will tell you -- is to watch the ball closely, making sure you don't jerk your head up at the moment of contact. STAND A RACKET'S LENGTH FROM THE NET TO VOLLEY: Great idea until your opponent decides to invoke the lob. Unless you're a Wilt Chamberlain, standing right on top of the net will make you a sitting duck for any lob or well-placed passing shot. Repositioning yourself halfway between the net and service line will give you the necessary "range" to field your opponent's toughest shots. AVOID NO-MAN'S LAND: The area between the service and baselines is not the place to camp out, nor is it the treacherous terrain some would have you believe. the compleat player handles shots in this zone with assurance -- advancing to the net behind the balls that land close to the service line and retreating behind the baseline on deeper shots. ALWAYS CHANGE A LOSING GAME: Sound advice if you get trounced in the first set by a decidely superior opponent. But if the margin of defeat is close, wait before pushing the panic button and changing your game plan. Consider that your tactics, like drop-shotting and lobbing an out-of-shape opponent, could turn off the tide in your favor in the final two sets. Q: I had a problem with tennis elbow last year and want to avoid a recurrence. Any suggestions? A: Avoid your backhand like the plague for the first 15 minutes of your warm-up and then opt for a slice or two-handed backhand to alleviate the stress. Use a racket that dampens those nasty vibrations -- fiberglass is best -- and stroke the ball as smoothly as possible. If the problem persists, consult a physician.