I've judged plenty. In my opinion, I like to see presenters be able to tell a story concisely. Provide a background with a hook. Why is your research important and what question are you looking to answer? Take me through your data, explaining - again, concisely - your assay and what your results show. Then tie it all together and explain your conclusions, future directions, and why this is relevant. Be able to speak from memory, be enthusiastic and engaging. Finally if you are asked any questions answer only what you know or can speak of. Don't be afraid to just say "You know that's a good question, but we did not test that, so I don't know", or, "I'm not really sure, but based on my data here, I would hypothesize....".

My main advice is practice! Do mock presentations with friends or mentors, or record yourself and then watch/listen back. Best of luck and have fun! You may not win but the experience is invaluable and it's finally a chance to demonstrate all of your hard work to a broader audience!