To add to what others said:
I usually use the WASD keys, sometimes the mouse, sometimes both at the same time.
Ditto on #3 above, use the terrain to slow down
You can 'cheat' and start the race 2 seconds early
The spider and wraith forms don't slide as much, keep bugging Q until he changes you into one of those
I like to jump the last few meters, it seems to make a difference if you're less than a body thickness behind.
I use crouch (C key) for an emergency slowdown. Use more on the multiplayer race.
After you've mastered control, try running with the ski boots as they are faster.