I did a lot of party ingame lately and I think create a group is the most helpful advise and lock the doors for everyone except the household, exception the room where you want them to be. Party location is a musthave, too. The easiest is the gala Diner I think so far I prefer the Prestige over the normal Event, because I can see what I can do for more points. The only problem I had so far with the camping and the kava party, I was so close to the Gold, but lag and thunderstorms prevent this. I had a good experience with 8 or 9 guests, who were very close friends to my sim. If you don't have or can’t use mods, lock also also the door to the toilet, for your own sanity.