My anxiety is the worst before, during and after presentations unless i have valium, klonopin or xanax. i used to have a few alcoholic beverages before i would do it which kinda helped but not really. try breathing excercises, they kinda work for me but my anxiety usually takes over.
I have a funny anecdote regarding presentations that may make you laugh, maybe not though. One presentation i had to do last semester involved explaining the differences between por and para completely in spanish and it had to be 25 minutes! I got anxious when i read about the presentation in the sylabus months before i was even supposed to give it. Luckily i found someone that could sell me klonopin the week before and i took 2 of them before the presentation and it went great. My teacher even told me that i should be a teacher because im so calm and relaxed when in reality i am the exact opposite.