You know your subject. In fact, you know it better than anyone in the audience. So forget about yourself when you're standing in front of a group, and instead really focus on your audience. Watch their expressions. Involve them in your presentation.
People retain interest at a much higher level when they are actively involved in a discussion.
Do not rely on notes. You need to be looking at your audience, not at your notes. It's okay to have a couple of 3 x 5 cards with a few sentences to jog your memory, but, remember you can't look at your audience and your notes at the same time. And it's a good deal more important to make eye contact with your audience. As soon as you hear about the opportunity to present, prepare a rough first draft.