What does ATC do during "slow" times? I know at larger airports, it's NEVER a slow time. But what about at smaller airports that are large enough to rate manned ATC, but things aren't always fast-paced, high-traffic like at JFK or DFW, etc. (say an airport like JLN (Joplin Regional))? 

What other duties do ATC personnel do when the traffic is light? Do they just sit and stare all day at the readouts, waiting for any one aircraft to appear and call in? Or are there other "busy work" items they do when things are 'slow' and they are listening for air traffic to call in for instructions?
Admin stuff, emails, chat with a colleague if you are not alone on shift, read up on (ever changing) procedures, eat, read a book, make sure the coffee machine works, meditate, watch TV. Anything goes, really, as long as you keep an eye on the radar and stay close enough to hear the radio and answer the phone. Of course, this is all assuming that there are literally no aircraft in the sector at that time (which happens regularily at smaller airports). Whenever you have any active aircraft, you obviously need to stay quite focused on that.