Back when being a Boy Scout meant something worthwhile there was a merit badge called "Wilderness Survival".
I took it as a kid, and passed, and then later, taught two versions of the class, one for basic 'if you get separated from a nature hike', and the other if you ended up out on your own for some time.
The suggestion above is good, but there is one I would put before them, and another behind.
First: "Be Prepared". Know yourself, and your own skills, and be able to take care of yourself first, and then whoever is with you, with what you have on hand. Which is why it is a good idea to have some basic 'gear' in your car at all times.
The one that I'd put after the others is: Be easy to find. Assume somebody is looking for you and you WANT to be found. Rig large signs that Look Out Of Place from the air. Which means if you have a can of paint, put "Nebulous is HERE" in large letters in the field.