Do not cut switchbacks or take shortcuts. Cutting switchbacks contributes to erosion and trail degradation.
Don’t even think about it! Pack it in; pack it out. Period. If for some reason you are unable to carry out your trash, ask a hike leader to assist you before you resort to leaving litter along the trail.
Don’t pick wildflowers, carve initials in trees, or in any way diminish the trail. Instead, take a picture to share with others! Take only pictures, leave only footprints.
Notify either the hike leader or the sweep if you need to leave the trail to answer a call of nature. They will give you as much privacy as possible, and ensure that you are not left behind, which can easily happen if no one is notified that you are leaving the trail.
In general, bike riders yield to both hikers and horseback riders; hikers yield to horseback riders. Hikers going uphill are working hard and should be given the right of way over hikers coming downhill. Sometimes uphill hikers will prefer to stop and let you pass coming down so they can get a short break. The uphill hiker should get to make the call.
Cairns, ducks, or little piles of rocks are not needed and contribute to many lost hikers. Markers pop up all over and serve no navigational purpose other than confusing those who, rightfully so, put their trust in trail markers.