I don't have a lot to add, as my kid is just now nine and I have different concerns with her than I would with a teenager.

FWIW I've taken her on day hikes since perhaps age five and spend a lot of time on how to not become lost and what to do if she does get lost. She always has a whistle and a few other "survival" items, which are more to give her something to do than for actual survival.

I'll take her off trail a way and have her tell me where the trail is, then lead me there. I give her the "hug a tree" talk and emphasize that should she ever truly become lost, to make herself findable (and use the whistle). It seems some kids hide from rescue folks, thinking they're in trouble. I also note her shoes so rescue folks would know what footprints to look for should the unthinkable actually happen.

With a teenager i'd at least discuss what each of you will do should you become separated. I'll guess the typical teenage boy will likely try to hike himself "out of trouble" and can cover a lot of territory in a short time. If you can make the hike itself a nature walk and pick a fun destination, you should have a great time.

Cheers,