Another thought...my son sometimes struggles with getting started on new things, or giving new things a chance. For example, he wasn't sure he wanted to go to a semi-formal 8th grade graduation dance because he wasn't sure what it would be like, if he'd be expected to actually dance, if he'd make a fool of himself and so on. What I do to support him is tell him, you're playing the "what if" game but you can't just ask the questions without answering them - finish the game.
We go through each of his issues that create anxiety and answer "what if". So, what if they play a slow song? He doesn't have to ask a girl to dance if he doesn't want to. He can use that as a chance to use the men's room, or check out the food table, or get some pop, or seek out his buddies who also don't want to dance. What if someone asks him to dance? He can say "yes" if he wants to, or can say, "no thank you" if he doesn't want to. If it's a girl he wants to encourage but he doesn't want to dance, he can say, "Thanks but I'm kind of hungry - would you mind if we get something to eat instead?"
For speaking list all your concerns that result in your anxieties...
What if people can't hear me? Start your speach by simply saying hello and asking, "can you all hear me well enough?" If they say "no", speak up and ask them again. You'll find the right volume for the room.
What if I forget my place? Maybe you will. Just tell people, "bear with me - I lost my place....here we go..." and move on. Nobody will care. Better to just be honest about it - it just makes you appear more natural and approachable.
What if someone asks a question I can't answer? Let them know, "That's a great question - and one I didn't anticipate. If you can write that down for me with your email address, I'll look into it and get back to you later".
You get the idea...just play through all your concerns and have a plan for addressing them if they do happen. You always have the option to say "I don't know" or to take a pause. And you can also have other people there to tag-team with - you don't have to be the only expert - if a question arises and a colleague is better versed, you will look like a team player to say, "I think I'll ask Ed to answer that for you because he is really the go-to guy on that issue...Ed?"