I hate to throw a wrench in things, but I have to disagree with asking him if he wants you to order for him. I find special treatment like that demoralizing and belittling. My advice is to treat him like you would anyone else. Just be patient with him when he stutters. Continue to look him in the eye when he does. Basically just don't make a big deal out of it. Yet don't try to pretend he isn't stuttering either. In fact, if it seems like he's comfortable with you a noninvasive question about it can actually be quite a relief for the stutterer.