Other Points to Consider
It should be obvious, but the sign-up desk should be outside of the hall where the event is held, not inside the door. Once a person is inside, it's hard to tell whether he or she has properly filled out all of the liability forms and paid their admission. And if you can't collect the money, you won't be throwing parties for long!
Figure 6: A busy Sign-Up Desk is a happy one
Other things I found that make the difference between an amateur and professionally-run LAN party:Print out individualized welcome sheets with the attendee's handle or nickname on the sheet and place it at their reserved seat. This helps the person quickly locate their seat without having to hunt for a row and seat combo. In addition to the convenience, it's also a nice personal touch.
Figure 7: Welcome sheets await new players
A welcome bag with literature from your sponsors and / or a helpful FAQ sheet. The FAQ could include an event agenda, food prices, important places around the immediate area like hotels, and instructions on how to get their computer connected to their designated power strip and connected to the network. The FAQ should reduce the load on your help desk in addition to being convenient for the players. I've seen some events even include a CD-ROM including commonly forgotten game patches - especially for those games that there will be a tournament for.