Beetle Adventure Racing
Floating Cars?
In Inferno Island, as the police Beetle, drive to the bridge with the large hole in in. Don't drive across it, but rather go to the side to get a clear view of the bridge. Now turn on your siren (Right-C) and wait for the computer opponents to cross the bridge. Instead of falling off like they should, they'll float right on across as if there were a road there. This also works in Sunset Sands at the first ramp in the course.
Cheap Computers
A very simple trick to do and an overly pointless one at that. But just to let you know, no matter how hard you try to ram a computer opponent off the road, you'll find that they rub up against in invisable wall made just for them. So, if you ever thought of pushing one of those little buggers into a lake or something, think again, you just can't.