Before you get to the long, high cables you have an opportunity to practice on 2 short cables. You practice the proper form (knees pulled up, ankles crossed) and how to slow down (legs spread wide). If after the second cable you decide you don't want to go on, you can walk back to the observation deck and take the tram down to the bottom. Be aware that at this point you will not receive a refund (as of this writing $66 per person).
After the practice run you are ready to go to the longer cables. I forget the lengths and heights of the cables, but they can be a bit overwhelming. I do know that the last cable is roughly 1/2 mile long and can reach speeds of up to 50 miles per hour.
It was the most exhilarating experience of my life. Really amazing. I would like to do it again some day.