The OP makes me quite nostalgic. I have posted before that my grandmother had a formal dinner party at least once a year.
When I was old enough, I was hired to serve at them. It's how I began learning to throw them. Yes, formal dinner parties require a staggering amount of preparation.
It's not just the meal, which has to be planned to adequately serve people with a variety of food restrictions, but also the place cards and the seating and the cocktails and the hors d'oeuvres. Grandma also made sure she had someone look out for her more reticent guests so that they would have someone to talk to and not be left out.
I am not sure what was my grandmother's preference and what was actually etiquette, but I would add:
1. Have someone at the door to greet the guests and take coats/purses.
2. During the cocktail portion of the evening, be sure they servers give every guest a chance to sample all of the hors d'oeuvres. Make sure one has an adequate supply of mixers for the cocktails
3. Check plates, glasses, and silverware in advance to ensure there are no cracked or chipped pieces and that there is a adequate supply (read: matched set) for each table.
4. Check, double check, and triple check the seating arrangements as well as the head of each table (note: my grandmother had 3 large tables she used and could seat up to 30 people at her formal dinner parties). It is crucial to select a table head that will look after everyone at the table and make sure each guest is drawn into a conversation.
5. Once a dish has been served, place it on the sideboard so that the guests can get themselves another serving should they so choose.