Each year we go to conventions and not even notice the hard working hotel employees that have to deal with thousands of fans over a short weekend. Yes, they are paid but consider everything that the hotel employees do to make our fun weekend runs smoothly. For every hotel worker you see there are at least 5 more you don't see - from the front desk folks, maids, chefs and waitstaff, security people, event personnel who make sure that rooms are set up and changed around for panels, dances and so much more. Please remember to say thank you and to tip those folks who deserve it. If someone goes above and beyond be sure to let them know that they are appreciated. We are not the norm but we can still be the nice, well mannered group that comes every year.
Below are some tips from the About.com webpage on Tipping.
It may be expected in many situations, but tipping is never required. Tipping hotel staff and drivers should be at your discretion, and should be thought of as a reward for excellent service. Don't feel obligated to give a tip if the service given was sub-par. On the other hand, consider giving a larger tip for those who go out of their way to provide personalized or stand-out service. Although it is not required, tipping etiquette says that unless service was severely lacking in some way, do give a tip of some sort (or at least a smile and a thank you).
For more tips and hints on tipping check out About.com.