Ironically, I stutter the least when giving presentations to large groups. When I was in school, I remember always calling in sick or making up excuses whenever required to give a in-class presentation. Sometimes I'd arrange with the teacher to do it just one-on-one. I absolutely hated doing them, they put so much fear into me. When I was in college I became educated and impassioned about a topic, and was eventually asked to speak in public on it. The first few times were a little bumpy, but after doing it more and more I got really great at it. Strangers would come and tell me what a strong and great public speaker I was. I can talk for an hour in front of a group of a hundred people with barely stuttering on a single word (meanwhile I still can't ask what's for dinner without stuttering). I don't have any tips or tricks to share though, but becoming passionate and knowledgeable about something gave me the confidence to put my stutter out of sight and out of mind (and out of earshot), I suppose.