The secret to a good bunker shot is in the set-up. Probably more so than any other shot. The quality of your basics in the sand will determine how well you play it.
Aim your feet and hips slightly open to the target to give room through impact and help cut across the ball. Lay the clubface open before you grip the club. How far you need to keep the club open will depend on the distance to the hole. The club needs to stay open to skim through the sand and maximise the bounce angle on the sole. Shuffle down deeply, below the fluffy sand, so you have a stable base.
The ball should be slightly forward in your stance in relation to your swing path. This will give you plenty of room to splash the clubface down into the sand behind the ball. Your weight should be fairly evenly distributed but slightly on your left side.
You need to take a full backswing, even from fairly short range. The reason for that is the sand you need to remove the ball is heavy and you need to splash it out. Your sand wedge has a lot of loft so you need to almost make a full swing to get the ball going forwards rather than straight up in the air.
You don’t need to be too precise about the point of entry into the sand – anywhere between 2 and half an inch behind the ball will produce a similar result. The worst thing you can do is hesitate – you need to commit to the shot and keep your rhythm.
You can vary the distance you hit the ball by opening your stance, the clubface or even changing your club but the length of your backswing and pace needs to be the same. Make sure you swing your hands back to at least shoulder height and then follow-through a similar length.