Trail Running Tip #2 - Remember to pick your feet up.
This is to avoid tripping over roots, rocks, and other fallen runners. It may seem obvious to lift your feet, but it can be easy to forget this, especially at the end of a long run when you are fatigued.
Trail Running Tip #37 - The sensation of blood running down your shin is a helpful reminder to lift your feet.
If you don't have blood running down your shin, try tripping over a root.