I agree with Chris. Don't undertake any search by yourself. Get help and stay where you can be available to the search crews when they arrive. They will have questions that only you can answer. If you are in the woods, they will have to work with limited information.

I did search and rescue in Maine for many years. There is a lot that you know, that you might not think important that IS important. Like does the lost person have any candy and if so, what type. We often look for food wrappers.

If there are many people in your party, you might have them do a "hasty" search. That means quickly check the obvious places. Walk the trails making noise and listening for a reply. But don't add to the problem by stomping off into the woods. If the probable area is small, station people at places where they can see long distances and just watch. Unless injured, most lost folks will eventually find a trail.

It is an almost overwhelming urge to dash into the woods and find a loved one. But in most circumstances you can do much more good by being available for the search crews.

Oh, and before you all leave on the trip, spend a bit of time talking about whistles. Be sure everyone has one. Probably the best single thing to help get found.