I found a handy glitch on the Planet Kalebo III, for the skillpoint 'Magician'
But I'm not sure if its the same on the NTSC version.
All you have to do is, when you're nearing the last jump of the track, go over the jump, but veer off to the left side towards the "U-pipe" and keep going in that direction so you're boarding into the pipe. You should be fairly close to the edge, and Ratchet will either go off the edge into the water, or fall off his board. Either one should work. It should take him back to near the start of the course, where you can do more tricks until you reach the desired amount. You can do this more than once in a race. I found it very handy indeed.