Follow up with the person and ask them what you can do to help support them. Indicate that you care. Stutterers are very self conscious of stuttering, so when they stutter don't smile or laugh or be impatient. Ask them to point you to more information on stuttering. If you see them being bullied or mocked, step in and support them. Simply taking the time to talk and listen goes a long way. Hmm, the things I wrote above are just what normal friends would do for other friends, just be a good friend.