While on your bike you must feel in control so that you will be prepared
to stop or brake at any moment. You should aim for an efficient riding
position which may feel uncomfortable at first, but you will quickly get
used to it.
Here are some tips:
Keep your weight distributed over both wheels; This will help with
traction.
Try lowering your seat post about a 1/2 inch to accommodate bumpy terrain.
Keep your head up and looking to spot obstacles.
Keep your arms slightly bent to absorb shock, and NEVER lock your elbows!
Your grips should be loose, but still feel as though you have control
over the handlebars.
Your handlebars should be about 2-4 inches lower than your saddle.
This is really personal preference.
Keep the ball of your foot centered over the pedal axle.