You need strength and swing speed when playing from the deep rough, but you also need good technique. The keys are to make a full backswing while keeping a quiet lower body (1) and to keep the right arm below the left during impact and follow-through (2). Here are some other things to remember:
Increase grip pressure, position the ball two inches back from normal and take a few practice swings to find the perfect descent angle to the ball—somewhere between a standard swing and a vertical downward chop. Practice swings also help in gauging the grass's resistance.
Hit mainly with the strong big muscles (back and legs), not the weak small muscles (arms and hands). Avoid severely chopping down on the ball by keeping your chest rotating through impact.
Too many golfers go for broke when a play back to the fairway is no sure thing. My golden rule when playing from the gunch: Avoid having to recover from a recovery shot.