for me I only bring up the fact that I stutter if someone comments on it or imitates it or sometimes even ask "are you OK?" or they'll sometimes think Im drunk lol, then I'll just tell them "No, I'm fine I just have a stutter." Usually after that people apologize for commenting or imitating, at which point I'll excuse them by saying something like "Oh, no worries its not a big deal" and smile or laugh it off and say "dont worry about it", "no problem" ect.