Tense moment: If your arms are straining (right), you're standing too far from the ball.
I see amateurs all the time standing so far from the ball that they have to reach for it. They grip the club and extend their arms stiffly, which causes tension in their shoulders. It's a big contributor to slicing because it promotes an out-to-in swing path.
I rarely see anyone stand too close to the ball. In fact, I tend to agree with Byron Nelson and Johnny Miller, who've said you can't stand too close to it.
To find your correct distance from the ball, get in your swing posture, and let your arms hang freely. Then bring your hands together. That's where you should grip every club in the bag. You want to be looking in at your hands, not directly down at them.
The distance you stand from the ball will change automatically depending on the length of the club. The longer the club you're holding, the farther you'll stand from the ball.
Your posture (spine angle) changes only slightly from club to club. You stand a little taller with longer clubs and bend over more with the shorter ones.
MORE THOUGHTS FROM TOM
When I was learning how to play, the only thing I was taught about sand play was to keep my left arm moving through the shot. Doing this kept me from digging too deeply with my right hand. This swing thought will help you take a shallower and longer divot, which is key to getting the ball out consistently.
Tom Watson is a Golf Digest Playing Editor and the golf professional emeritus at The Greenbrier, in White Sulphur Springs, W.Va.