I read this nice article about stuttering. They said this: ● Instead of telling the stutterer to slow down, set the example by speaking more slowly yourself. Listen patiently. Do not interrupt. Do not finish sentences for him. Pause before replying. ● Avoid criticism and correction. By appropriate eye contact, facial expressions, body language, and comments, show interest in what he says, not how he says it. ● Stuttering should not be a taboo subject. A friendly smile and an occasional kind acknowledgment of the problem can put the one who stutters more at ease. Perhaps you could say something like this: “Sometimes it is not easy to say what we want.” ● Above all, convey your acceptance of him as he is. I try to do these things when i meet someone who stutters. Except i start to get nervous and then i start stuttering a bit more, and i don't want them to think I'm mocking them, so i just don't say anything.