Trail running is an inherently dangerous activity and thus being the case, don't be an idiot. Always make sure you sure that you adequately prepare for all of your adventures and most importantly use common sense. You know, check the weather, dress appropriately, tell someone where you're going and when you plan to be back or even better find a running buddy* so you can get lost together.
I've tried my best to to think through all the possibilities but anyway I do make mistakes so if you find a problem, let me know! I recommend studying the routes and elevation profiles before you leave so you have a good idea of what kind of terrain you are supposed to be covering.
*dogs don't count in this case unless your dog can use a cell phone