While this article is aimed at Uber or Lyft, I think it can apply in general.
Perhaps the most important is:
Consider Forming A Driver Safety Network
Small groups of drivers around the country have beginning forming security networks, usually using a group chat service. Basically, you have a number of drivers join a group in Google Hangouts, WeChat or another messaging service. Then, when you go out driving, you simply keep the chat window in the background. The idea is that if you have around ten or more drivers in a group, there will usually be someone else driving while you are. That way, you have someone you can send a message, or broadcast your location to, if necessary.
This goes with making sure people know where you are at. Sometimes, one may not be able to have a precise location, when providing roadside assistance. Thus, especially for after dark and predawn assignments, making sure others know where you are is vital.
You may be able to use other things, ranging from sprays to tasers to exercising your Second Amendment Rights. It is your responsibility, in such situations, to make sure you are in accordance with all applicable laws, ordinances, etc.