One aspect of golf that clearly separates amateurs from pros is their ability to play out of bunkers. The best Tour players can get up and down from greenside sand about 50% of the time. Few casual players, even low handicappers, can boast that kind of average: Bunkering an approach shot usually spells bogey or worse.
Although most amateurs can execute a successful explosion shot, they lack distance control. They either explode too long or short, leaving a lengthy par putt. If you spend a little time improving your distance control from sand, those par putts will start to get shorter.
Three factors determine how far a sand shot will travel: How hard you swing; how far behind the ball the clubhead makes contact with the sand; and how open the clubface is. Simply put, the harder you swing, the farther the ball will go. The closer behind the ball the clubface strikes the sand, the farther the ball will go (there is less sand to cushion the blow). Finally, the less open the clubface is, the less effective loft it will have, sending the ball lower and farther.
The simplest way to gauge distance is to keep two of these factors constant while varying the third. Most pros prefer to change either the force of the swing or the amount of sand taken while keeping clubface alignment consistent (though they may open it more for exceptionally short shots or square it up for very long ones).
The easiest way to regulate the distance of an explosion shot is to alter the force of the swing, keeping clubface alignment constant and taking the same amount of sand every time. It's the same principle applied to half-wedge shots: The farther from the green you are, the harder the swing should be.
If you choose this method, determine how open you want the clubface and how much sand you're comfortable taking. Then keep those two variables constant and practice exploding different distances by modifying the force of the swing.
A more advanced method of gauging distance on explosion shots is to keep the swing force and clubface alignment constant while modifying the amount of sand you take -- hitting closer to the ball to make the shot fly farther, farther from it for a shorter result. Many pros favor this method, but it can be tricky for amateurs, who don't practice as much. That's because the closer behind the ball you hit, the greater the risk of catching it cleanly (taking no sand at all) and sending the shot well past the target.