Don't let him smoke too much at first if he does decide to. Give him a couple hits, then 5 minutes later ask him how he's feeling. Then ask him if he wants to smoke more. If not, just let him be. Make sure you're there to comfort him in case he doesn't like it.

My first high was fucking insane. I took 10 or so hits of mids, not knowing how much I should smoke, or what it would be like. Not surprisingly, I freaked out and almost swore to never do it again. Thankfully, I gave it another chance, and have since loved it. Anyway, just make sure you introduce it to him smoothly.