I think my house is haunted. What should I do?

That depends on the degree and kind of haunting.
If it's just a lot of rattling doorknobs, faint moans, phantom footsteps and the occasional blood-curdling shriek, you don't have much to worry about. I generally deal with that by drinking beer and hiding out in my garage office. Normally, that's all it takes to establish an understanding.

On the other hand, if you've got blood oozing from the walls, flying cutlery, and doorways to Hell randomly opening and closing in the broom closet, that's another matter entirely, and stronger methods are called for. I pack my shit (and beer)and head for the lake. Then I get drunk. I've just never had much luck with exorcists, personally - a lot of the time, you call the ones in the Yellow Pages and they never even show up to give an estimate.