Make a first good impression. When meeting them, give a nice smile, a firm handshake, and your first and last name, if you think it's appropriate. Maybe tell them something about yourself, and mention who you are in relationship with your friend with, whether you are working on a science project, or are boyfriend and girlfriend.
"Hi there, Mr. Mann. I'm Grace. Kayla and I have been working on our science project for a few days now. We'll just be upstairs, working. It's nice to meet you!