Take an improv class.
I found Dale Carnegie to be helpful. And nothing beats repetition.
But to tell the truth, I only really started to relax when I realized that very few people in the audience actually cared, and those who did care, cared only about the facts, and the facts were in the handout, so I could relax.
Try the propanolol for the physical symptoms, until you’ve done a few presentations and feel more comfortable.
For presentations, a lot of good has been said here: make it as interactive as the setting allows, encourage questions and dialogue, so it feels more like a conversation. Take almost everything off the slides - the important thing is what you’re saying, so keep it to a few points (1 or 2) and a relevant graphic and then talk them through it. You can send out the speaking notes version later, but while they’re in the room with you, keep them engaged.
and, yes, practice. Know your material cold. Someone will ask you something completely irrelevant - what are you going to say? Just be prepared for how you’re going to handle the unexpected. It is ok to say, I don’t know, I’ll have to get back to you.
FWIW, one of the best things I ever did in business was to take a seminar on giving presentations. They videotaped me. It was hell. And it make a huge difference. Consider asking your manager to sponsor that for you.
I used to REALLY hate speaking in front of a group. Now, its no big deal. However, I know my subject matter really well and give the same presentations week after week after week…It took several repetitions until I was really comfortable. I speak with confidence because I AM. confident. Which goes right back to knowing your material.