Here is my advice since I sometimes ride the trails alone. Always let someone know where you are going. Take a cell phone with you. I also carry a multitool with a knife on it. Maybe I'm paranoid but I like having it. Be aware of your surroundings. Carry a spare tube and know how to change a flat and a light if you are riding in the evenings. You don't want to get stuck out on a trail with a flat in the dark.
Just some ideas.