Never leave a job interview without collecting business cards from each individual who interviewed you. You'll need their email addresses for following up and want to be clear on the spelling of their names for any handwritten thank-yous.
And while we're on the topic of following up: remember to ask if there's a time line for filling the position. This question is for your own sanity. While the time line could very well go out the window during the hiring process, it allows you to gauge when it might be acceptable to follow up with an email asking about the status of the position.
So, next time you interview, don't give your final handshake until you've received business cards and asked the time line question. You'll save yourself from having to call the company's reception to ask for contact information, not to mention the mental cushion of having a time line to help you decide when it's OK to make the second follow-up move.