Practicing is very important. I usually tell the presentation a few times when I'm alone and after it a few times in my boyfriend's/other friend's company. It decreases the stress of the general "presentation" thing, only the stuttering will stay. Plus, my first sentence in every presentation is that I say it out loud: I'm stuttering, so it might take me more time to finish my words and my presentation. This way they can also figure out what's going on and I'm less stressful because I know there won't be any shocking disasterous surprise, I feel like I'm 'entitled' to stutter.