If you find that your ball is in the bunker, but you are standing on the outside of the bunker, you can pretty much guarantee that you are going to have a difficult stance. You are likely going to be standing above the ball, so you need to be careful with your stance.
The first thing you want to do is to access the lie. Are you going to be able to clear the lip of the bunker? Are you hitting from soft sand or do you have to dig at the ball because you are laying in hard sand in the bunker? This obviously matters in the type of swing you make.
The next thing you want to do is to widen your stance, so you are lowering your entire body a bit. You want to bend from your knees in this instance, do not bend from your waist. Bending from your waist will not allow you to swing with your upper body. For this type of shot, you should keep your legs and feet still and swing by using your arms and shoulders. Stay centered over the ball and let the club slide under it, as you would normally do when hitting out of the bunker. Take your stance away from the ball and take a few practice swings. You want to simulate the actual shot in this instance.
One of the mistakes many amateurs make is that the practice swing does not mimic the real shot. If you are hitting outside of a bunker like the above scenario, or hitting on a downhill or uphill lie, you want to take the actual swing you are going to make prior to hitting the ball. Being off by just a half of an inch when you make impact with the ball is going to cause your trajectory to be off significantly. Remember, when you mishit a shot like this, the longer the ball travels, the more off-line it is going to be. So if you hit it 150 out of the bunker, but miss-hit the ball by an inch, you may find yourself in a different fairway, or worse yet, out of bounds. Simply practice the swing you intend on making before you take your actual swing. For more tips, be sure to check back with The Texas Golf Trail daily and watch your golf game improve with every round.