I can not stress 8 and 1 enough. There's no reason to hide the elephant in the room, just go ahead and expose it and get that over with. I had 2 classes last semester that were nearly 90% presentations/group work. One of the classes it was only 3 presentations throughout the entire semester. The other one was one every 10 days or so. I rarely prepared for the one that made me do one every 10 days and I stuttered a lot more than the other one. For the other class I practiced with my groups multiple times, had fun, laughed and I was able to edit some words with something that I'd be able to say just fine or with minimal loss of fluency. Practicing is the most important thing you can do.