One of the most effective ways to institute those changes is to make practice swings in front of a mirror in your garage or basement. In many ways it’s superior to hitting balls on the practice range, because you focus more on getting into the proper positions—which always feels awkward at first—than on worrying about where the ball goes. I’ve actually found that visualizing the flight of an imaginary ball after each swing is great mental exercise. Another variation on this is to close your eyes when you swing; that fires up all the other senses and often leads to new insights.
Better players will probably benefit the most from moving through their positions in front of a mirror, because they have a more subtle understanding of the swing. But everyone, no matter their level, will gain in terms of their physical conditioning from repeatedly swinging a golf club. Sometimes I even wore gym clothes to the garage. Fifteen minutes of swinging hard can produce a right decent sweat.
I had great success with this approach during the winter of 1991–92. My specific goals were to keep my chin pointed at the ball during my backswing and to add width to my backswing. But in the course of doing that I also realized I would do well by setting my wrist cock a little earlier. I worked my tail off in my garage that winter, motivated by the desire to win the Masters in April. I didn’t, even though the pieces came together quite nicely in Augusta, but I did go on to win the British Open that year.
For golfers able to practice outdoors, even if conditions aren’t ideal, I can suggest a few other great winter projects. One would be to master wedge play. I’m amazed at how dreadful many amateurs are on shots from between seventy-five and one hundred yards. If you focus on that for a couple of months with the help of a pro, by springtime you could be scoring five strokes better.
It’s also possible to develop a touch for chipping over the winter. If you can’t practice at the range, simply practice chipping to baskets or other targets. You can do it off a mat, if necessary, or indoors into the couch, or with a Wiffle ball over the couch. I’m also a big believer in the value of carpet putting. At the very least you can work on honing a smooth, rhythmic stroke. If your carpet gives you a true roll, you can work on aim and even distance control. As a boy I spent millions of hours indoors playing "putting billiards": I would putt one ball to hit another in such a way that it would knock a third. That’s a fine way to develop dead-eye accuracy.
If you live in a climate hostile to winter play, plan a visit to a golf school or schedule a buddy trip for the middle or late winter and let it function as motivation. If you aren’t in decent physical shape for golf, a five-day school will snap your body in two; if you’re limber and reasonably strong, it can work wonders. And buddy trips can stand as a good test of the changes you’ve tried to make in the garage.