Yield right of way to cyclists and horseback riders. Give hikers and runners a verbal heads up before passing. Your earbuds volume should be low enough to hear other trail users.
Always yield to cyclists on singletrack, its much easier to step aside as they pass. Turn earbuds down to hear impending cyclists for your safety and theirs. Use caution when running around corners and over hills.
When coming upon the heels of hikers, let them know you intend to pass as not to startle them. Doing this in a friendly demeanor goes a long way.
When an unfamiliar dog approaches, stop and make sure the dog has good intentions before continuing. Stopping dampens the dog's instinct to take chase allowing you to gain more control of the situation.
Crossing paths with a skittish horse can be a risky encounter for all parties involved. If you happen upon a horseback rider, stop running and look to the rider for advice on how to proceed.
Never discard gel wrappers or any other kind of rubbish on the trails we love and play on. Make certain to leave no trace, use available rubbish cans or pack it out. Responsible use will ensure future access for all of us.