The most important thing you can do is not panic. Take a break, eat something, and then reassess your situation.
If there you know where is an open area with visible view of the sky that is close to you, go there. If you can start a fire to keep warm,and it is safe to do so, then start one. Fires can be smelt by searchers and the smoke can be seen by both ground and air search; and more importantly it can help you not become hypothermic. If hypothermia becomes an issue, you will become more disoriented.
Don’t move. Moving increases the search area drastically. For example, going down Mt. Pilchuck not only increases the search area in radius, but the total area is larger as the mountain becomes larger the lower you go. The mountain also blocks radio and cellular signals.
Only move if you have to, staying put may not feel productive, but it can reduce the time for us to find you.