My usual big party is Thanksgiving. Occasionally, I stray over to New Year's Eve. More than six for dinner is stressful. Eight is traumatic. The tips I have learned to keep it under control:
1. Keep the food simple. No last minute take-it-out-of-the-oven tricks. No last minute sauces.
2. If it has to be rewarmed, make sure the recipe forgives inexact timing. You don't want to be serving dessicated mystery food to your guests.
3. Have more silverware/napkins/cups/tableware than you think you need.
5. Have a system worked out for what to do with the dirties: silverware, plates, serving dishes, etc.
6. Have several areas set up for food so that everyone doesn't crowd one area.
7. Enlist a close friend or two to help with the details. Bartender? Wine pourer? Dishwasher?
8. Be explicit in your invitations: Starts at X time, lasts til X time, bring (or don't bring) XYZ. Also discuss attire.
9. Assign a greeter so that you aren't running back and forth to the door, interrupting your prep.
10. Simple but effective decor makes a great party. Themes, flowers, iParty, color. It is subliminal and it works.
11. Have fun. Your guests will have less fun if they see you not having fun.