Picture this scenario: You're cruising along on a string of good holes when you knock an approach slightly off line into a greenside bunker that's so deep the wall towers above your head. Don't worry, you don't have to play out laterally. The correct technique will enable you to hit an explosion that flies high, easily clears the lip and lands on the green.
It's All in the Grip

To get the ball up quickly, you must exaggerate some of the techniques of an
explosion shot, especially the grip. Slide your hands down the grip until your
right thumb and index finger wrap around the metal. Turn the clubface wide open
until it faces the sky, then weaken the grip position slightly, which will
prevent the club from closing on the downswing.
Keeping the clubface open, aim it down the target line and open your stance the same way you would for a standard explosion shot.
Spread your feet wide -- slightly more than shoulder-width-apart -- and bend a little more at the waist to make up for choking down the club. (If you don't widen your stance, you'll have to bend even deeper at the waist, endangering good balance.)
Playing the Shot

The hands must be extra-active in this shot. Pick the clubhead straight up
with a quick break of the wrists on the backswing, then hit hard about an
inch-and-a-half behind the ball.
The harder you hit down, the higher the ball goes, so don't be afraid to use some force. It's better to be a long with this shot and on the green than short and still in the sand.
A final tip: Don't leave the clubhead stuck in the sand. Strive for a follow-through. Otherwise the ball will die into the face of the bunker.
Quick Pick-up Drill:

To get the correct feeling for breaking the wrists quickly on the backswing:
Private Lessons 1999 Times Mirror Magazines, Inc., used under license by GolfServ Online, Inc. Instructional information provided by Golf Magazine.