I used to fly these beautiful contraptions myself and it's as close as you can get to human flight, imo. It's also one of the most dangerous ways to fly since the canopy can easily collapse if you're not careful. A lot also depends on the weather conditions, the configuration of the terrain and the wing itself - these are generaly categorised from 1 to 3, 3 being the most demanding (control and safety wise), hi-performance gliders. Pilots tend to exploit the thermals, columns of hot, rising air, to gain height, or as in this video, the technique called ridge soaring, relying on the lift provided by the air which is forced up as it passes over the ridge. If the conditions are good, you can stay up there for hours... There are also a number of techniques for controlling and fast descent of the foil, some of these are described in this wiki article:
http://en.wikipedia.org/wiki/Paragliding