Larry,
Each singer's song request is typed on a seperate request slip. The singers can then take the packet to their table and sort them, choose their next song, throw away what they don't want etc. We allow them to bring up as many requests slips as they want at one time, just have them in the order they want to sing their songs. We keep all requests slips turned in and during the last rotation my wife sorts them and get them ready to put back into the plastic bag. As the singers leave for the evening they drop off their zip lock baggie at the KJ desk and we insert the collected request slips.
All this works smoothly because there is two of us working the show. My wife keeps the rotation in order and walks around to smooze the audience. I am free to banter with the crowd and the singers over the mic and keep tabs on the mixer board and the computer.
Hope the info helps. If I can be of any further help, just ask.
Gary