Thanks everybody! Wow great responses here.
wonmyfts - First thing I'd like to make clear, this is the XBOX version of H2. I have no idea about the PC version. Updates don't matter, mine has the 1.1 map updates and sword fly removal. Every one of my videos is directly recorded from an original Xbox console, but the same stuff would work on a 360 I'm sure.
The easiest corners to ride are ones with a 90 degree shape. A perfect "L" shape. You can ride both sides of it, but I found usually one side will be easier to ride than the other. However, you can still ride both. You want to avoid being right on the "point", pick one side or the other. You can move to the left and right during the fall, hold forward and press against the corner, or is some cases you can fall and survive without moving or doing anything once you are in the right spot. Also, at least for riding in Metropolis, you have to be able to get the banshee to the last zone at least once. I have about 10 profiles with banshees there, because I wanted checkpoints in perfect spots to practice really hard rides.
The video I made explains it and shows examples, thanks to Grumpy for posting it but here it is again:
http://www.youtube.com/watch?v=uYKhUEl_Q5s