I would show him some of the milder stuff, think choking, etc. Try to lead by example with dirty talking. It's super awkward until you get the hang of it, but there's tons of porn online that he can use as an example (video and written). Communicate through anything you try, and try to guide him to do whatever you want him to do. Ask if he's comfortable. After sex, tell him how much you liked when he did ___. Best of luck!