JimmyMack's description of the dismount is good. His Step #3 is crucial for maintaining stability, although he forgot to mention that you should move your right hand to grip the top tube, not the brake hood.
Sometimes you don't want to thread your right leg through and forward. If you're going really slow towards a barrier, which often happens in bottle-necks during the first lap, or when you approach a barrier on a hill, or when you're just too tired to go fast, you might want to leave that right leg back, otherwise you could get jambed up and fall over before you can unclip.
I have a few comments regarding Step #5: One, if you push down slightly on the top tube while you unclip, it helps unweight your left foot, and makes unclipping a bit easier. It also gives you a little boost when your right foot hits the ground. Two, if you intend to dismount and shoulder your bike, as you unclip your left foot and step down with your right, as soon as your right foot hits the ground (or thereabouts), slide your right hand down past the left side of the top tube and grab the down tube. From there it's just one quick motion to get the top tube up on your shoulder.
Some people (like me) prefer to switch around the brake cables, so the left brake lever operates the rear brake. This allows you to apply the brakes while standing alongside your bike without the threat of locking the front wheel -- this has saved my butt a number of times.