Play the ball forward in an open stance.
To help you hit the sand first, set the ball just forward of center, with your hands slightly ahead of it. Open your stance to promote a shorter swing.
Always open the clubface at address.
An open face will increase the bounce on the sole of the club so it doesn't dig deeply into the sand. It also adds loft, which helps get the ball up quickly.
Break your wrists early.
Limit your arm swing as you hinge your wrists in the takeaway, then try to maintain that hinge through impact. Your hands should lead the clubhead at all times.
Maintain clubface loft through impact.
Don't rotate the face closed--you'll bring the leading edge into play and dig. Through impact, hold the face open so it keeps the loft you set at address.
Accelerate through the sand.
Hit through the ball, not at it. Both arms should straighten in the follow-through, the club pointing at the target.