I agree with what everyone else has said. To add, I think you should have some concrete examples of times that you've demonstrated:
1. Time Management
2. Critical Thinking
3. Success in managing multiple tasks at once
4. Team Player
I find that in research, these are the most important skills to have because there's so much day-to-day stuff on top of the science and you really need to be able to get that out of the way to focus on your research.
In general, I would say just read up on the topics and issues that they are studying, and also the research going on at the institution in general and be able to talk about it in layman's terms. No one expects you to be an expert but it shows that you've come prepared and are interested. Also this goes without saying but be super nice to everyone. I feel like 80% of my job is sending emails and working with others and I find that dealing with someone who has a less than friendly personality can really throw off your groove.