If you've ever been to one of my bunker classes, I always start the session by doing a drill. This is very common to what Rory McIlroy does. It involves drawing two lines. One will be for the feet which will be aiming considerably left of the target while the other will be perpendicular to this line. You then want to set-up behind the feet line to a stance slightly wider than shoulder width apart. You should have the perpendicular line right in the middle of your feet.
The perpendicular line will be your entry point for the club. What your aim will be is trying at impact to contact the front part of the line. At the start you can just focus on just hitting the line but then you can be more specific and hitting the front. At the set-up as mentioned before when playing bunker shots, make sure you have 60% of weight on your left and maintain this weight all the way to impact. You should also be hinging your wrists on the backswing to create enough power when striking the sand.
When you're doing this exercise if you notice that you strike the sand before the line, it will mean one of two things. One is that you're not keeping on the front foot right up until impact and the other is that you might be unhinging your wrists too much early on the downswing. Ofcourse if you strike the sand after the line it will mean that there's too much forward momentum on the follow through.
The other element of this is that you want to feel like you're slapping the sand and not digging. Having the face 'open' at set-up and all the way to impact will ensure that you slap or thump the sand. Once you have successfully worked on this drill, you can then take your ball and place it in front of you. With your finger you can draw a little line about an inch behind the ball. Your goal is to hit that inch behind the ball.
If you have any trouble coming out of bunkers just let me know and we can book a bunker lesson.