Be confident on what you are speaking about - practice it until you know it almost off-by-heart.

Take notes. Everyone forgets things sometimes.

Speak slowly where possible - remember that you know what you want to say (hopefully) but the audience may need more time to process it.

Speak loudly but don't shout. If you have the option of a microphone try to avoid handheld ones so you can flip through notes or activate remote for slides.

Try to scan your audience where possible so it looks like you are speaking to them, not just reciting.

Always keep in the back of your mind that you judge yourself way more harshly than anyone else will. I've spoken at many events and meetings and I can still remember times I got something wrong or did something I though was embarrassing. I've seen many more people present and I can't remember any specifics of the times they have made mistakes although I know some made errors (I just can't remember when or who). It's human nature to be self-conscious but you can learn to get past it with practice and perspective.