First, you spend a good 20-30 minutes with a great safety and instructional video that spells everything out very clearly. Then, you are assisted onto a Segway and you practice doing it. If you have ever skiied, you are at an advantage as the shifting of body weight makes bumps and maneuvering corners effortless [and much less risky than being on the slopes, assuming you pay attention to what you are doing!]
My tour (no one else there; i had a lucky solo!) was led by Bill, a personable man who gave me attention and confidence and steered me clear of danger, while talking quite knowledgeably about the interesting sights we were passing by.
The Segway driving part was FUN FUN FUN! No real physical exertion involved except standing for an hour or so (they take short breaks) but you have to be conscious of your surroundings because you are on city streets most of the time! Try it!! Well worth the price! I am going to look for Segway tours in other cities too now!