It's good if you can find a bike rack that has a really low rail on it. There are some that have a rail that is flat, about 10ft long, and about 4 inches off the ground. Great way to start. Remember to keep your feet a little wider than shoulder's width apart, and keep your balance right in between your feet.

If you have the money, you can go to the Home Depot or Lowes or some other hardware store and build yourself a practice rail. If you do, make it so you can adjust it so when you get good, you can set it to a slope or higher up.

If not, then use what's around you. When I was camping, I made a bow staff and found that it can double for a practice rail. It's about 7 feet long so it does okay, but it's not flat so it will wobble.

Also, a very helpful tip: Use whichever handedness you are. Like if you're right-handed, lead with your right foot first and vice-versa for left footed. You can do it however you want, but going by handedness would make it easier on you.

One more thing: Make sure to bend your knees. Bending your knees helps you maintain your balance. Put about 60% of your weight on your back foot so you have more control over what you're doing. It's ALL easier said than done, but as with everything; it comes with practice. Good luck!