IMO, one of the worst things you can do is film a bunch of areas and things that AREN'T going to be in your haunt. It sets people up to expect whatever you show in the trailer. Even if it's a good show, if they don't see anything in the haunt that was in the video, they will likely be disappointed.
Try to get 2 or 3 rooms of the haunt done and use those. You don't have to have the entire place finished to shoot a trailer.
Operations Manager & Technical Director
We're headlining the HauntCon 2012 tour! We hope to see you there!
A big thanks to all of those who came out to visit us on the '09 MHC Pre-Con Tour!