I've heard about driving up walls before, but have never previously accomplished it.
The biggest difficulty is that you need to get all the wheels on the wall at once, if a wheel comes up off the wall at all, gravity will take over.
I've discovered that it's particularly easy to do on the upper loop at Wardill airport, since there's a sloped glass edge which leads directly to a section of wall.
Gravity still effects you a little, and the car has a tendency to pull towards the ground. If you turn the wheels, the car will start moving; and if the car isn't exactly level, the car will slowly move forward as if on a hill.