Practice practice practice. In my program I took we had to take a public speaking class which included 10-12 presentations infront of the class. Best way to avoid a storm of stuttering from being nervous is studying the material you are presenting and REALLY knowing it. I found that when I came to areas where I forgot what I was going to say next, I would try to fill in the blank space with whatever popped in my head and that was when the stuttering would kick in. Rehearse, rehearse, and then rehearse again.