Maybe you don't hear it much because he only speaks when he feels he won't stutter. There's not too much you should do other than being patient and including him since you don't want to be responsible for his sociability and communication, he needs to learn those skills on his own. But one thing my friends did that I really appreciated was if we were at a party talk to people or meeting someone new, they'd either introduce me or when I introduced myself and the other person didn't understand, they'd repeat it. They knew I was OK with that or I'd give them a look if I didn't want to bother repeating it. But honestly, just standing by him when he's stuttering and acting like it's no big deal is helpful enough because it shows other people the right way to react to stuttering.