I guess it depends on your skill set. If he has not gotten off in a few days you may want to let him have a free pass before you really get started even help him out a bit with it. I am a big fan of any girl who can do a strip tease. So if you can pull that of let him do his thing while he watches and maybe a hand job or blow job to get a quick one off. Then show him what to do to you to make you feel good while you give him some time to get hard again.
You should not make him nervous. Give him control and let him do it at his pace. You could also tell him how you like it and even if he is not that great do tell him that it was great to have sex with him. That would give a boost to his ego.
Understand he is most likely going to be completely lost. Without making it totally obvious, guide him through it, take control but let him feel like he is in control. Let him know what you like before hand. Be dramatic (not kverly dramatic) when he is doing good. And dont show disapponitment when he is done quick.