When addressing a group, think of it as similar to speaking to one person... just more people. Your presentation tells a story and the audience most likely wants to hear (and, in the case of visual aids, see) that story.
Speak deliberately and in a friendly voice... don't go all "school marm" on them by treating them as lesser beings. Think of them as friends and acquaintances.
Do not stand with your feet together... bad form that sets you up for wobbling.
Do not stare one one part of the audience; scan the entire audience slowly - eye contact is a good thing.
When asking a question as part of the presentation, it should sound like a question. Conversely, when presenting a statement, it should sound like a statement.
If using visual aids (i.e., PowerPoint, etc.) carefully check spelling, context, and grammar for accuracy before the presentation and while practicing... you will
practice and review your material beforehand, right?
Of course, do not say, "um" (with whatever number of m's), "uhm", and the like... save those for typing stuff on the Internet where many do not care. Again, you have facts and/or ideas to present; state those points and back them up with verifiable facts, and you will have the audience in the palm of your hand.
Now, go and kick booty!