I used to do this weekly for a job I had; the best way to do is to learn your subject matter inside out and practice like crazy. The people you'll be speaking to are just people and you're simply talking to them. No different than sitting on a couch in someone's lounge telling a story to a crowd of people. Propanolol will work well for sure but in the mean time, learn your shit inside out. Practice in front of the mirror, family or friends.