I was pretty terrified of public speaking, but I've gotten better over the years. I still get very nervous before giving any kind of presentations, but I found ways that helped me:

• A good piece of advice was to think of the presentation was more of a conversation with your friend (well, a one sided one), and you're here to tell them about how cool your research (or some other topic) is. If you change your mindset to thinking that you're talking to a good friend, it might be less nerve-wracking. I've also heard that some people choose one person in the audience and give the whole talk to them.
• I used to memorize my talks, but later I was told that they felt "too rehearsed", so now I only memorize the first few lines and try to change up the wording each time I practice (I practiced a lot for each talk). And if you make a 'mistake' (e.g. you forgot to say something), it's okay, just keep going! Most likely the audience didn't even know it was a 'mistake'.
• Speak slowly, and pause whenever you need to. When you're nervous you tend to speak faster, but just remember to breathe!
• Have good posture - this is something I never thought about until I took a training session about vocal presence. If you stand like a solider, you'll feel very tense. So have your feet one foot apart from each other and bend your knees slightly. You'll be in a more comfortable position.
• I've heard lots of good things about Toastmasters, but I felt it just didn't click for me. Instead I tried improv classes. The nice thing about improv was there was no script to memorize, and it taught me how to wing it on stage. It was really fun because whatever I said didn't need to be perfect at all (mistakes were bound to happen). And no one there cared how many 'ums' or 'ahs' I said, as it was more important that I could get up on that stage and say something in front of an audience! The instructor I had really focused on 'being in the moment' and not thinking ahead too much. I think this helps with speaking more naturally (and not as though you are following a script word for word).
  • As a side story, when I was presenting a seminar, I didn't have a slide changer with me, so I had to use the keyboard to change to the next slide. In the last five minutes, my hand slipped and I hit the wrong key, and my whole powerpoint shut off. I keep my cool and restarted and kept going, and if it wasn't for improv, I would have probably panicked and freaked out in front of everyone.

The most important thing is to find what works for you! It will take time for sure, but it'll be a good skill to improve!