To those of you who stutter: what is the ideal way for someone you don't know well to converse with you?

To those of you who stutter: what is the ideal way for someone you don't know well to converse with you? I don't stutter, and have only known a few people with very mild stutters (I didn't notice that one guy who I see fairly often until my fiancé mentioned it to me after I had known the guy for a couple of years!). I recently formed a study group for a two-year professional certification program and one of the guys in my (seven-person) group has a pretty severe stutter. I didn't notice it the only other time I met him (it was a very brief interaction). Last night he talked a decent amount but not as much as everyone else, and sometimes he would get stuck on a word for a very long time. I wanted to act in a way that would make him as comfortable as possible, but honestly I have no idea what that would be. I'm sure to some degree it depends on the individual, and also on the situation. Sometimes someone would eventually suggest the word they thought he was looking for, though we also all did this to each other in general. Other times we would all wait for him to finish, but I can't imagine it feels good to have six relative strangers staring at you for 45 seconds, albeit kindly and patiently, while you struggle to find a word. So, what is the best way for me to act around him to help him not feel uncomfortable? Also, how self-conscious do long-term stutters tend to be? Do you think it's something he's always painfully aware of with new people, or something he's kind of used to and doesn't stress about it too much? Thanks!!