Could you explain a bit more about the "try-hard" part? I think I might've done that during one of my classes and it turned off a potential PI.
You are making this alot harder than it supposed to be. All of the things WedgeDawg mentioned are from people trying too hard. The two biggest things to know going in are a) how to describe your research experience in succinct way while giving a clear takeaway message of what you gained and learned b) talk about your future plans and your goals and if asked how this lab ties into them.
What kind of "interview" is this?
Are you an undergrad just trying to volunteer in a lab? If this, it will be rather informal in most cases, just look and act competent.
If you are a college grad looking to get a research assistant job it'll be a little more formal and it'll be key to answer the two questions I mentioned above well and you should be able to highlight your strengths and skills.
Now the key thing here is
YOU are the one who should be asking the key questions. What kind of time commitment are you looking for? Duration? What kind of projects have undergrads in the past gotten involved with? Who will I be working with; other students, post-docs, PhD's etc? Do undergrads get their own projects(and if so what kind of timeline is it ie do they have to start from the bottom and work their way up or do they get thrown in soon) and what is expected from them? Have undergrads gotten in papers in the past in your lab? These are the first things I thought of, you can come up with more.
Make sure this is a productive lab experience above all else. See if the PI is talking about just getting you "exposed" to research and being in a lab or talking about specific projects and things you can do. Some PI's simply think an undergrad physically being in a lab, watching things, washing dishes, cleaning things and other labor is good experience. Others are far more interested in what they contribute in terms of project work. Get a feel for the PI. If he gives off a bad vibe or seems unconcerned with your interests, note it. If you can meet other people in the lab, especially whoever is designated to work with you, note that as well. Don't just rush into a lab because it is the first one that agreed to take you.