Depending on the terrain see if you can locate a pair of gators to help keep your shoes from filling with debris. Even the smallest grain of sand can feel like a boulder.
Your focal point will need to be a little shorter - but you still need to scan up the trail. You may have roots, soft areas, rocks, and water to deal with. Watch the hips of the runner just in front of you. That will give you a clue as to whether they hit a hole or are making an evasive move.
Your stride may need a little modification..... you may need to pick up and set down your feet instead of gliding like many runners do. It will use more energy so you may need to slow up on the trail.
Most of all, good luck and HAVE FUN. When I lived in Houston we had a few trail runs in a state park north of the city. The races were fun...