There are two schools of thought, both work, but for different shooting situations.
Sling Position: Using the sling to support the rifle, and in High Power or Small Bore Shooting. The sling does the work in supporting the rifle, and distributes the recoil throughout the body. If done right, you fall back into position with your NPA after recoil. The tighter the position, the less effect of recoil and the faster you get back on target.
It's best to go to a CMP GSM Clinic or Appleseed event to get coached in using the sling. Go to the CMP bookstore and get a copy of the AMU Service Rifle Guide ($6.95).
The second, witch is used in long rang precision rifle shooting is referred to as "driving the rifle".
What this amounts to is getting straight behind the rifle. Under recoil the rifle comes straight back. No angle what so ever. Your body absorbs all the recoil equally. As you fire, the rifle jump should not to the left or right under recoil, but straight back. No lateral movement at all of the muzzle.
A good way to practice this method is get a shooting mat, or piece of tarp to shoot off of. Draw a line straight down the center of the mat. The where you elbows set, draw a line across the mat making a perfect Cross.
Line up so your body and rifle is straight down the line you drew down the length of the mat. Place you elbows on the lines that go across the mat.
As you shoot, the rifle will come straight back with no muzzle movement to the right or left.
Again it would be best if you could work under a coach to learn this method, baring that Jacob Bynum, Rifles Only, puts out a great DVD "Precision Rifle -Disk 1, Fundamentals" .
I would highly recommend this DVD to anyone, old or new, who is interested in precision rifle shooting.
A bit off topic now: I'm a high power shooter, I use the sling and NRA or CMP positions, either in competition, practice, sighting in and hunting. Been doing it for a long time (competitively since 1977).
When I use to hear the term "driving the rifle" I always laughed, "you drive trucks, you shoot rifles".
When I got and studied the Rifles Only DVD and found out you can teach an old dog new tricks.
The Method taught by Jacob is in fact driving the rifle. He compares this method much like you would drive a car. An example (If I can do this without infringing on copy write material) is, as you drive down the road, you don't think about going straight. Put your hand on the steering wheel, you don't make drastic changes guiding the car. Slight unconscious movements of your hand keeps the car going straight.
Same with the rifle.
Bynum shows the comparison in keeping the rifle straight, hence, no muzzle jump to either side.
Again, I'd recommend the RO DVD to everyone who shoots a rifle.
The DVD covers other items, related to precision rifle shooting aside from the OPs question.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071