If you use your right foot, I would suggest you to take your brake off unless you use your right foot at the back.
Here is how you do the trick:
1. Raise your right foot to the back while going at a normal speed, so you are standing on your back wheel.
2. Then, raise your left foot so the front wheel of your rollerblade is standing up. So, in other words, it is exactly the opposite of your right foot.
3. When you are in this position, try to stay balanced, and don't move your feet or else you might do another a artistic trick that won't be so comfortable, and then fall on your butt. That could easily be painful.
4. Now, after doing that, if you want to get down, put your left foot back into its normal position, and do the same with your right.