Just make sure the fog machine won't set off the smoke detector. Nothing kills a party faster than blaring loud beeping...
Which reminds me, the #1 thing to ensure a good house party- Make sure your pills are good. Use a test kit! The first ever house party we had we picked up Mario Stars... notorious pipes but we didn't know. We had the music, multiple rooms, awesome lights, fog, soft things, all the good makings for a wicked house party... but everyone had the worst night of their lives because of those shitty pills.
Oh! And the guest list. It's always tempting to tell your friends "invite whoever you want!" but it's a pretty good idea to know who's coming. Again, having some shady ass friends-of-friends walk in can be a downer, especially for the host. Or having that one drama queen that always gets WAY too fucked up and kills the vibes.
Also, if you're not cool with other drugs besides E, be sure to let people know that. Some people seem to think that just because illegal activities are going on in that house that they can break out whatever drugs they want. If you're not comfortable with that, let them know before hand. Same with alcohol. Super drunk people + rolling people isn't always a good mix (yes, i can be, but not always.)