Make sure you speak clearly and that you take the time to ask your audience if they have any questions. It is important to cover everything briefly, even your failed attempts, and to do so in a logical pattern. Don't spend too much time on one thing. If you are working with a partner, take your turn explaining the project and switch every five minutes or so. This way, it allows your audience to differentiate between sections and will add energy to your presentation.
Teamwork is essential.
Work together and help each other out. Other Don't participate in science fairs for the awards. Don't do science for the recognition. Don't compare yourself to anyone else and don't force yourself to do it. Do it because you love it and because you can make a difference.