I never had to talk for that long, but I had quite a number of presentations in college through the last year or two. My method is practicing at home, giving a presentation to myself. By doing that I kind of get used to those sentences I am going to say which makes it (at least for me) easier to say when the time for the real presentation comes. While presenting I like to kind of avoid direct eye contact, but that also can seem weird, so I like to stop from time to time to take a breath and make quick eye contact. Just so it doesn't look too weird... That's all I have. Hope it helps! And don't worry. You are going to nail it! Good luck :)