Wedge shots, whether from hard sand or soft, must not be forced. They must be played with an easy, lazy swing in which the sand is used as a buffer to poofff the ball out. And, of course, to get results you must follow through and complete your arc.
If you are in a trap where the sand is reasonably soft, aim to hit a spot about two inches behind the ball. The wedge will do the rest.
If the sand is hard or wet, you cannot hit so far behind the ball, because the packed sand will offer too much resistance and your wedge won't be able to travel through the sand beneath the ball as it must. In these conditions, you should aim at a spot about an inch or so behind the ball. Swing the club a little more upright and use a shorter swing and follow-through. You may have to use a little more power than when you are playing from soft sand but not much more. Keep your swing essentially lazy.
Now, if you have a bad lie, say, a lie in a footprint, you've got to waive the no-power rule and hit this one hard. You aim at a spot just behind the ball, use an upright swing with no pivot and hit forcefully—as if you were trying to bury the clubhead in the sand beneath the ball.
Phil Taylor, Victoria Golf Club, Victoria, B.C.