This is a very broad question, but there are a few things that stand out. First, content is always crucial. Your content needs to relate to your audience and purpose, and should be substantiated thoroughly. Your content should always connect with your audience as well, so that they are interested and engaged. If the content is assigned, it should address all the requirements, and you should draw in something unique and fresh in your talking points.
Beyond content, a good oral presentation will be well thought out and organized. This doesn't necessarily mean that you will write out everything word for word, but you should at least have an outline connecting your points and keeping you from wandering off track. Good presenters make eye contact with their audiences and make their audience feel welcome and comfortable. If you are nervous, don't let on. Your audience will feel more at ease if you present yourself as confident. Smile, look at everyone, and make them feel like they are participants rather than observers. Finally, a good oral presentation is articulate. Use standard English and appropriate vocabulary. Avoid filler words ("um," "like," etc.). Speak clearly, and if you stumble simple correct yourself and move on.
These are, in my opinion, the basics of any successful oral presentation.