Ok here goes
Wear a long sleeve black tshirt with no logos
Black pants that are comfortable and easy to move in
black shoes and black socks
Bring a gallon of water to drink (yes a gallon)
Bug spray (in case you are outside)
throat losanges (you might yell yourself hoarse)
aspirin or Tylenol (your preference, you will be yelling and near loud sounds, better to have your
own then to leave your station and miss groups for a tiny pill or two)
baby wipes (to remove make up- I think it best to have your own)
IF YOU HAVE ASTHMA BRING YOUR INHALER
Bring those things in an unobtrusive gig bag and they will think you are a pro.
Here is a tip on what to do.
Report to your house manager, do not screw around during instructions, do not bring your phone to show (leave it in your car) Find out what they want you to do, and do it. Most haunted houses will allow some experimentation in order to find out what works and what fits best in the room your in.
Be those things and they will love you, I know I would.
(most of this is on my actor training DVD, you may want to invest in one or two of those mine is good but I wont say its the best,be careful there are some stinkers out there that just give bad advice.)
Best of luck this season,