give em a proper joint or a bong hit. in case of bongs/pipes, they should smoke at least .3 (or 3-4 decent bowls).
I don't know about you guy but .3 is just a little over a bowl at most. You can never tell how much in grams because you don't know if they are inhaling properly. Just smoke them up out of a pipe or bong if you can. Also the amount is whatever it takes to get them high.
If it's good weed it shouldn't take more than a gram per person if they are smoking right, but then again it is more for some people. If it's some mid grade I would say get 7 grams just to play it safe. If they don't get high their first time and want to stop throughout the process it is fine. Not everyone gets high their first time. Getting high for the first time might be a fight for some people, but a fight that you will definitely win eventually.
Junk food! Food they like. Pizza. Sodas. WATER is good for cotton mouth. You will definitely get it. Are you one of the first timers?
He is one of the first timers so I'm sure he doesn't know how to roll a blunt, not that it wouldn't be the perfect learning experience though. He could go buy a 2.50$ joint roller and roll a perfectly cigarette shaped joint.