This is what I've been thinking to do so far:

To express interest: Introduce myself and get a convo going, and then one minute in create a silence, then look at them and say "hey, you're pretty cute". Maybe you guys have a better way. I'm really shit at expressing interest in a natural way. Saying "I came to say hi because you looked pretty cute" just doesn't sit right with me because it seems robotic. It sounds socially uncalibrated in a college setting for me, unless I say it after warming them up a bit. I could be wrong though, and would appreciate insight.

When rejected: With regards to getting rejected, I'm thinking of shrugging and smiling and just saying "your loss, have a nice day".

Edit: So ask open-ended questions and then smile and say "have a nice day".