Out on the trails, the right-of way rule is that bikers yield to hikers, and both yield to horsemen.
To put the above into practice, take the advice put forth by a consortium of Oregon trail user groups. They say: Stop, speak, and smile.
Here is a link to a video explaining the Oregon group’s alliteration: Stop Speak Smile
Some horses are easily startled, so people should say something as soon as they see them. Bike riders who meet up with horses should stop and move their bikes off the trail.
While hikers may notice bikers first and step aside, bikers are again expected to stop and clear the trail.
When bikers meet each other on the trail, the rider going downhill needs to stop and let the climbing rider pass. The biker who is passing should share how many are in the group to help the waiting cyclist decide whether to wait or not.
Stop, Speak, Smile.