Despite my problems with nerves and anxiety, I've given many successful presentations and talks to groups of people in my professional life. There are some things you can do to help yourself.
Be organised about your topic. Make sure it has a concise introduction, middle and conclusion. Take time to plan it out in advance. Don't busk it!
At the beginning, maybe say to the audience that you're a little nervous. This will help the situation. Do it in a light hearted way. It somehow takes the pressure off of you. Say something like, "I'm not a professional speaker by trade but, hey, I'm still going to give it a bash!"
Are you using Powerpoint or slides? If so, having entertaining visual aids is always a good thing. Having acres of text on screen is just boring. Do a bit of Googling for some fun images that relate to what you're talking about. It always puts a nice atmosphere in the room, if people maybe laugh a little or see something colourful. You can then add to the image maybe a few key words that will remind you of where you are and what topics you're meant to be covering at that point. This will help keep you on track.
It's been said earlier, but do practice. It helps a lot. Also draw up a list of possible questions that you may be asked and have some answers in your head, in anticipation of them.
I sometimes use appropriate music in the introduction. There's a song for every topic and situation. If you're doing a biology presentation, for example, and you're covering the circulatory system, why not use "Heartbeat" or something like that?
Speak slowly and in a measured voice. Engage the audience. Don't do all the talking. Ask them to chip in and maybe put a few people on the spot. Take the attention away from yourself from time to time. Give them tasks to do, for example, talk amongst themselves for a bit about what you've just said and get a bit of feedback. You can have a slide on screen whilst you're doing this that says, "Over To You" or "The Floor Is Yours", or something like that.
Wake up earlier than normal the day before so at least you'll be so tired the night before you'll get a good night's rest. Pick an outfit you really like or are comfortable in the night before. Have it all ready for when you wake up. Don't create any additional stress on the day.
Go to the place you're talking in well in advance and get set up. Make sure things are working and the room is how you like it. Maybe open a window near to where you are to keep you cool or install a fan beneath the desk or near to where you are, discretely and out of sight. Whatever makes you comfortable.
You'll be fine. Try to make it enjoyable for yourself and the audience. Be creative. Be relaxed...and go for it.
Let us know how it goes.
