And then target two or three sims to socialize with repetitively to make sure they're having a 'good time'. Enough decoration in the target party area for a mood boost is a good idea. Make sure there's free food laying around, and conversely enough toilets.
Five to seven is about my manageable leve, I don't care about party crashers. I've found the only way to make my parties a 'success', was to follow a set formula.
