Everyone else pretty much has it covered.
Adding my experience here - I was lavaliered even though my boyfriend (now husband) wasn't greek.
He had heard about the whole lavaliering/pinning thing, and asked me for details. A few days later, he presented me with a little heart-shaped pendant as a lavalier. My sorority had a candle pass for me just the same as if I'd gotten a fraternity lavalier. We never quite got to the pinning stage - we got engaged first.
So you don't have to miss out if your boyfriend isn't greek.
Oh, a "date dash" (at least at my school) wasn't just a date party... it was a date party where you had very little time to find a date. "It's Thursday... we're going out to dinner this Saturday, bring a date." Usually means the social chair messed up...
