If I'm meeting a teacher/professor for the first time, I find it helpful to self-disclose and be upfront but nonchalant. Something along the lines of, "Hey, I stutter, so it takes a little longer for me to say what's on my mind sometimes." My fear of stuttering in important situations creates a lot more anxiety for me, making it more likely I'll stutter. In my case, I think it's a fear of being judged. I think that's a form of social anxiety?