Teresa Nielsen Hayden, who has run innumerable successful publisher-parties at science fiction conventions, has just posted an incredibly detailed HOWTO for running a successful large room party at a con:
Get in as early as possible. Turn the thermostats to "Lunar nightside" and the AC to "Siberian blizzard". You're going to have a lot of radiant bodies in the room. Start laying down a basal layer of cold now.
Give yourself prep time: order dinner from room service.
You have a moral obligation to feed your party prep minions, if you have them.
If you're in a very nice suite, remove any fragile ornaments to the top shelf of a closet. Remove all the phones (except for one, if you're sure you'll need it) to a dresser drawer or closet shelf. If you're staying in the room, secure your possessions.
Optional: rearrange the furniture. If you're using the big conference table for refreshments, move the chairs away. They'll do more good over by the sofa and easy chairs, and removing them will keep social maladroits from sitting there and chowing down on your munchies.