A polite way of saying "I know you, but I don't like you well enough to make definite plans, so I'll leave you thinking that I at least considered having a night-out with you."
Oh my God..Sarah?? Wow, long time no see! Hey, I can't stay to chat, but we should definitely do something sometime!
What a person says when they see an old aquaintance that maybe they met once or twice, and that they thought making out with was a good idea at the time. You may or may not remember their name, and this is what u say when they want to get together.
Them: Hey! Oh my god, you're looking so hot. Here's my number! I never got yours... how funny.
You: Um, hi. Yeah, I'll take your number. We should do something sometime. *coughcough