I used to be deathly afraid of speaking in public to both large and small audiences. Including even giving presentations to small groups of fellow engineers in my field. I never really studied any techniques or solicited advice from others about how to overcome that I just kind of worked through it myself. This is what I found that helped me.

The first and most important thing is practice and rehearse. This is especially helpful for a lecture style presentation where you're either not accepting questions or questions come after and can be in an informal setting rather than a formal question and answer. This allows you to rehearse the role as if you're acting and muscle memory can take over. The danger here is that it can sound rehearsed but generally that's because you've rehearsed it too little. You'll notice actors and actresses when they have a role that is well rehearsed they become so good at it it appears natural because they've rehearsed it so much it sounds kind of silly to think of it that way but that is the way it works. To little rehearsal makes it sound rehearsed a lot of rehearsal can make it sound natural.

Avoiding questions as part of a presentation is another thing that I did in the beginning because when it's free form it's much more difficult to control and understand what's going to happen. So you can get easily flustered and distracted. Moving the questions to an informal or to an after-presentation one-on-one or very small groups of people who are interested in their questions makes it a lot easier because now you're engaging in a conversation. Depending on your speaking opportunities that may not be what's desired so your mileage may vary on whether you can do that.

Finally the last thing that allowed me to become really comfortable with it is coming to the innate understanding that everybody makes mistakes and the audience is on your side. The audience doesn't want to be bored to death so you have to be engaging in entertaining but ultimately the audience is for you and rooting for you and wants you to succeed in your talk. They are there to learn from you and engage with you in a positive and constructive manner. Even if they're critical of your talk or conclusions it is still a constructive thing. Of course if you're a comedian that may not be the case because some people will be there to heckle you but I'm assuming you're mostly engaged in technical talks where that's not the case. Once you can grasp internally that the audience is with you and not there to embarrass you they're there to learn from you and they want to learn from you that helps a lot. Think of yourself when you're the audience member if the presenter stumbles over their words you don't care because you're there to engage with what they're speaking about. Ultimately as an audience member you want to make them comfortable so you can absorb the information. Your audience wants the same thing from you. That is a really hard thing to internalize because we do have the natural fear of getting up in front of people and we naturally feel embarrassed if something goes wrong. So it is difficult to overcome but once you can move to that stage everything gets a lot easier. this makes the question and answer periods that are free form a lot easier as well. Because now you're not worried about making a mistake or potentially saying something in error. You have the confidence to be able to say I don't know or I need to learn about that more or even solicit information from other audience members on something you're not as familiar with.

This moves you into that space of getting out of those jitters because in your head you can associate this as a conversation but instead of one-on-one or three to five people in a small group conversation it's one to 100 but it's still a conversation.