Downhill bike races can be very tough to shoot the first time.  Athletes are whizzing by in excess speeds on uneven terrain, and dust is flying, all the while you are trying to get your settings correct and find an angle that doesnt put you in danger or interfere with another photogs angle.  

Here are some tips to help you nail your first (or 100th) DH bike race shoot!Don't ride your bike to get to location.  Once the race starts you'll be stuck in that spot or you'll need to weave your way through the woods carrying your bike and all the gear.  Hike down the course.  It may be a pain, but it'll be way easier then attempting to bike a live race track.Limit the amount of gear your bringing.  One to two flashes will suffice.  You won't need studio gear in spottily lit forests, often times hot shoe flash at 1/16 power will be perfect!Start at the top and work your way down.  We usually ride the lift up and then hike down along the edge of the trail.Use the ski run nearest the trail to get down to the best parts for shooting, trying to hike the trail can be a nightmare.Scout the trail first.  Know where the gnarliest parts and best corners are.  Remember: The rider doesn't need to be moving super fast to make a great photo, the terrain will make the image stand out!If it's not raining and hasn't very recently, the trail can get dusty.  Find a dusty section and frame to show the dust flying behind the rider for drama.
Don't bring traditional lightstands.  Trails are uneven.  Get a tripod at wal-mart or target for $20.  It will be lighter and have adjustable legs for the uneven trail.Bring ball bungee cords.  They look like a small loop of bungee cord with a ball on the end and are perfect for strapping a flash to a tree!Once you have your flash and camera setup, move to new locations without packing that gear again, just carry it in your hands to save a ton of time.It's best to shoot multiple angles and get diverse images.  As soon as you are happy with the shot you get from a location, move to a new one.Keep your eyes open for unique angles.  (i.e. climb a tree, lay on the ground, whatevery makes your shots different!)
Shoot in locations where other photographers are not.  This gives you an advantage because your shots will be different and stand out from the pack.