Buffet service is the only way to go for catering, at least as far as we are concerned. Our local chamber of commerce sent us a request for a quote for their annual awards dinners, table service. We declined to bid on that one. My lovely step-daugher just got married last week, it was a very high-end event, and even that one was buffet service for the reception dinner. No, we did not cater the reception, just the rehearsal.
The contract is the most important tool of communication. I have learned that when people start asking you to do "just one more thing" I start adding those things and the labor costs to the contract. I used to bend over backwards to more than was contracted for and my staff almost mutinied
I made a last minute, small change to the menu for a reception we are catering this weekend, but only because it was an option for that particular item when we first set the menu and wrote the contract.
P.S. I have often been asked about cake cutting duties. Some caterers charge an amazing amount for cake cutting. I tend to give them a good deal, since I would be there anyway while my crew is normally cleaning and packing while I cut the cake. But still, put it in the contract!