After many years of problems with Pistols, this paragraph has helped me much. 
- Paul

c. Isometric Tension. The firer raises his arms to a firing position and
applies isometric tension. This is commonly known as the push-pull method for
maintaining weapon stability. Isometric tension is when the firer applies
forward pressure with the firing hand and pulls rearward with the nonfiring
hand with equal pressure. This creates an isometric force but never so much to
cause the firer to tremble. This steadies the weapon and reduces barrel rise
from recoil. The supporting arm is bent with the elbow pulled downward. The
firing arm is fully extended with the elbow and wrist locked. The firer must
experiment to find the right amount of isometric tension to apply. 

NOTE: The firing hand should exert the same pressure as the nonfiring hand. If
it does not, a missed target could result. 

Quoted from 
FM 23-35 CHAPTER 2 ( Markmanship Training )
http://155.217.58.58/cgi-bin/atdl.dll/fm/23-35/FM23-_3.htm#REF3h2   Htm format
http://155.217.58.58/cgi-bin/atdl.dll/fm/23-35/ch2.pdf            Adobe format

which is part of
FM 23-35  COMBAT TRAINING WITH PISTOLS & REVOLVERS, 03 OCT 1988  
http://155.217.58.58/cgi-bin/atdl.dll/fm/23-35/fm23-35.htm          Htm format
http://155.217.58.58/cgi-bin/atdl.dll/query/download/FM+23-35     Adobe format