What I sometimes do is find a quiet place to prepare about 15 minutes before if I can. I close my eyes and take lots of deep breaths, and then read aloud to myself for a few minutes, slowly and with lots of "breath" and soft contacts on the start of all my words. During the presentation I try to make eye contact with most of the audience, but if I start to feel more stressed I focus on the person in the room with the friendliest face. I know if I stutter it's not the end of the world, the sky won't fall, and I just keep going!