How do judges evaluate presentations at an undergraduate conference?
I apologize for the length of my reply, but I think this is a really great question that I discuss with undergraduates and even grad students all the time, and want to use this as an opportunity to share some of my thoughts with you.

I completely agree with the points that Fábio Dias made in his answer. However, I want to add one general tip with you that I have found to be extremely effective in my experience both presenting talks and posters as well as judging them.

The way I see it, when undergraduate talks/posters are judged, there may or may not be certain specific criteria against which you will be evaluated, but there are certain important subtleties in how you conduct yourself when talking about your work that will almost always affect your evaluation whether there is specific criteria or not. Let me clarify:

As Fábio Dias mentioned, there are many important technical factors that are commonly taken into account when judging presentations, but aside from this, I believe that one of the most powerful tools to get great scores on research talks is to demonstrate some passion and interest into the work you are presenting.

This is typically the biggest problem with undergraduate presentations. Undergraduates are often not very well-versed in the big picture of their research project and therefore end up simply presenting what they did and what data came of it and what they think it means (or what their advisor told them it means). There is rarely any visible interest in the work, or evidence of creative thought on the part of the student, and this is the biggest factor that separates a great undergrad talk from all other undergrad talks.

No matter how dull your research talk may or may not be to you, when you stand up there in front of all those people, make sure to talk and act like you're the most excited person in the room about the work that you have done. This gets people's attention, in my opinion, above all else. Some great ways of doing this are:


Never, ever, ever, ever, ever read from your slides, especially your
title. Always come up with a great "prose" way to describe your whole
project and then your data.
Try to look at your slides as little as possible, unless you're pointing out something on a figure. Look at the
audience, glance around the room. In a scientific forum setting,
simple presentation skills often directly translate into command of
the material being presented.
A great way to prevent yourself from doing the above is to not have
many words on your slides, this keeps people interested and keeps you
from reading to the audience. Many undergrads believe that their research cannot be presented without many words on the slides, but there is almost always a creative way to do this.
Question yourself, and question your research. This does not
mean you should tell the audience that your conclusions are not
accurate, but rather avoid being too rigid in how you describe your conclusions. Avoid words phrases like 'definitely,' 'clearly,' 'this means that,' 'we discovered,' or any version of the word prove/proof/proved, unless used as a technical term such as 'mathematical proof.'
Always talk about your work in terms of what it could mean for the
future, For example, talk about some interesting data that you
couldn't yet explain; offer several possible ways to frame your
conclusions; try to add a few "next steps" to your presentation (and not as a list on the last slide, but work it in in a few places as you talk about your work).
If you anticipate a question or questions from the audience that you
will probably not know how to answer, bring it out in the open as
part of your presentation, and say that you are still working to
understand that particular part of your project.


Some of these things may seem trivial or obvious, but these are probably the most common "mistakes" undergraduate students typically make when giving oral presentations. I say "mistakes" lightly because it is obvious that sometimes the student simply does not get the proper guidance from their advisers, either about their project, or about how to present the work properly, or both. In these cases, of course, acting like you truly love your project may not be possible because it may not be true.

But either way, what it boils down to usually, coming back to something Fábio Dias said above, is that at the undergraduate level, the expectation is less on whether the results are impressive, but rather whether you can demonstrate that you are a good researcher, and that you have done the most with the results that you have.

Good Luck!