He comes by it naturally. Harmon’s father, a club pro at courses in New York and Florida, did the near impossible in 1948: he beat a field of elite touring pros to win the Masters and wear the green jacket. Today all four of Claude Harmon Sr.’s sons are ranked among the game’s top 100 instructors. Butch got there by an indirect route. Frustrated by his golf game, he dropped out of the University of Houston to join the army in 1963–but not before angrily heaving a borrowed set of his father’s irons into a water hazard. (Claude Sr.’s response: “At least you could have joined the navy so you could get my clubs back.”) Later Butch knocked around the pro tour for three mediocre years. “I had the game to be good enough,” he says. “But I was too temperamental.”

Now head games are part of his shtik. Witness his new, Santa-sanctioned book, “The Four Cornerstones of Winning Golf,” written with John Andrisani (255 pages. Simon & Schuster. $25). In his unusually clear and succinct view, the game comes down to four basics: ball striking, the short game, the mental side and physical conditioning. In an interview, the Tiger trainer shared some of his commandments–they’re identical for women and men–with NEWSWEEK:

Practice the short stuff: Most golf strokes are racked up within 100 yards of the pin, not back at the tee. “The average player’s short game is terrible, and he has no concept that this explains his high score,” Harmon says. “I can move any 90 shooter into the low 80s in a day just by explaining how to pitch and chip. Golfers don’t practice those shots. They run to the range and pull out their drivers because they all want to be like Tiger Woods.”

Take some lessons: Most average players are embarrassed to do that because they think they aren’t good enough. “What’s frustrating for us is that it takes no athletic ability whatsoever to have a good grip or good posture,” Harmon says. “But if those are incorrect, you’re probably doing something else incorrectly just to hit the ball.” He suggests that golfers practice adjustments to their swings with 8 or 9 irons; at that shorter club length, it’s easier to get the feel of changes in your mechanics. And be sure the pro teaches you how to putt: “So many high-handicappers have poor mechanics–their heads are moving all over the place, they slide the ball back and forth in their stance. It sounds trivial, but when we just show people the right position, they score better.” Not to undercut his own book tour, but there are as many flaws in a golf swing as there are golf swingers. Players need individual advice. The book is a nice supplement.

Don’t be a pushy golf parent: It’s fine to let a child swing away at the driving range and then take a spin on the course. But hold off on lessons until age 10 or so, when Dick and Jane have healthy attention spans. Harmon and his brothers began swinging a club at age 6. But Claude Sr. raised his sons much as Earl Woods raised Tiger, with the freedom to take golf or leave it. “Our dad never pushed us,” Harmon says. “If the child doesn’t show some enjoyment of his own, the lessons won’t work.”

Buy clubs that fit: One size doesn’t fit all. Ask a teaching pro to help. Have him gauge the architecture of your body as well as your athletic skills and flexibility. Then take his advice over to the local golf warehouse–or ask the pro for help buying a good secondhand pair of clubs if a new set is too steep. “The club head is more of a cosmetic question. Get something that feels good when you take a few practice shots. And be sure you give the clubs a tryout before you buy them, just as you’d test-drive an automobile. A $500 driver is great, but not if it’s the wrong club for you.”

Often the toughest challenge for Harmon is what’s between a golfer’s ears. During lessons, he tries to discreetly size up a student’s tolerance for long hours of hard work. The payoff can be dramatic. As a rule, a 95 shooter with average athletic ability can drop close to 80–provided he or she practices for one hour three times each week and then plays on the weekend. (If they don’t golf, break that regimen gently to your spouse and children.) Even with dedication, it’s crucial to have someone skillful teach you right from wrong. Practice, Harmon says, makes permanent. It’s perfect practice that makes perfect. For more help, he’s got a couple hours free next month in Houston. The doctor is on the course.