I heard of this thing called "power poses". Before going into a situation, stand tall and put your hands on your hips for two minutes. It's supposed to help your confidence. I'm going to try it. Hunching over your phone texting is bad 'cos it is a submissive pose. I used to get really nervous, I still do. I try to remember that it just doesn't really matter! There are so many people in the world, I'm only inhabiting a tiny part. I also practice a lot, & imagine myself doing well. Imagining yourself doing well creates a positive memory in your brain & makes you feel good. Imagining yourself doing well (in great detail) over & over is proven to be almost as good as practice in itself. Imagine yourself doing well & imagine the feeling you'll get after doing an exceptional job! Worrying does the opposite, it provokes the feeling of failure & is a rehearsal in your brain of failure.
Think about the importance of the talk or lack there of. Once you say your bit, people will go on with their lives as if it never happened. You have nothing to lose by going up there. If you aren't confident, just fake it. Go slowly and take your time. Going slow is actually the key. The slower you talk, the less you will have to say to fill up whatever time requirement you need to meet. If you can use videos as part of your presentation, it can also help eat up some time. Practice usually helps. Do your speech in front of your family or friends before you need to do it in front of the class. If you are giving the same speech for the 10th time it will be easier than if you are doing so for the first time.
I dont think it is necessarily about knowing the people -- it is knowing what you are talking about. If you are confortable with whatever topic you will be talking about in front of them that will make it a lot easier. I used to be the same way (still am to a degree) but my confidence went way up when I started doing presentations about topics i was interested in.
Rehearse and rehearse again. Far too many people think that they can 'wing' it, but once in the situation, any number of factors can throw you off. Be as knowledgeable as you can possibly be with what you're going to speak about and then rehearse it again.
I was that way as a teenager, but I got over it. Perhaps it scares you because you do it infrequently. Overcome stage fright the same way that you overcome any fear, such as overcoming a fear of parachutes. You expose yourself to it gradually. If you had to talk in front of a group, every day, then you would overcome your fear quickly.
Make jokes... say funny stuff. That usually helps me. Nothing that would offend the teacher or professor though.
If it is a large group try to focus on an individual, not the roup. Just look at a single person and speak to them After a few moments switch to a different individual and so on. Remember you are in charge!
JUST PICTURE Y0URSELF A L0NE IN Y0UR R00M ARE BATHR00M.