My advice to most trail users is this:  Carry a cell phone and bear spray, both work on a number of possible problems.  Don't use earbuds in both ears, at an utter minimum keep one ear for your surroundings.  Groups, particularly for women are smarter.  A dog is a good addition, even smaller ones can be an asset. In reality, the more common conflicts I encounter day to day are from moose and loose dogs.  If your all zoned out with tunes it's far too easy to not see that moose by the trail.