In addition to being nice and to saying "thank you," as TR suggests, some of us learned that if we could cajole Ms. "What? Me hurry?" into showing us how to change the toner, add paper, or whatever else we needed to do, we didn't need to bother her. The same holds true for ordering desk copies, calling for travel reservations, or whatever else is nominally in the administrative assistant's realm: if she (or he) is busy, and if it's not a usurpation of his or her power to do it yourself, do so and lighten the load, unless there's some kind of status war involved that you don't want to be part of.
And yes, say "thank you."
This isn't the interview process: your new colleagues already decided that you fit in to some degree, or you wouldn't have been offered the job. They are probably giving you something of a popularity rush right now as everyone tries to get to know you. This will drop off in a few weeks, but not because of anything you said or did; it's just that everyone gets busy.
Speaking of busy: I have yet to meet an academic (or anyone else, for that matter) who responds well to any intimation that he or she is not as busy as you are. This seems to infuriate everyone without exception. Yes, you'll be really busy, but to complain that you're more overworked or have less free time than X to X's face is