This evolved from my own desire not to upset some people who happened to have just paid me to be my customers.
I tell them that this house has a long "Haunted History" and that the things I will be telling them are all true, no fiction. (They are true)
I point my flashlight on my face allowing them to "read" my expression, hoping to put the point across, no smirk, no clown smile.
I begin the history and eventually make a device activate in the room that scares some, makes others laugh, obviously a "device" that I had everything to do with, not something from another plain of existance.
Then I point out that I have just given their mind an "out"if they want to or need to make use of what I just gave them.
"What I told you is true, but if some part of your mind can't possibly handle it , the distraction and the humor of the recent incident gives you the opportunity to tell yourself, "It's all just made-up Baloney because look at how he chose to "punctuate" his serious, "true" ghost story".
The amount of time I am telling this haunted history usually begins to convince them yet I really do not want to cause severe consternation at a basic level of their personal belief system. I am not trying to "sell" a quasi-religious belief system here. I am just telling them what has happened here, in this house.
I offer up several theorys on the "why" of haunting, trying to appeal to the logical or even the scientific part of our brains, which could also act to lessen their deep fear of the unknown. I really do not wish to have someone flip out from what I am telling them here.
Make of it what you will.
I know some people will see and hear my words and praise my "acting". Such a compliment misses it's mark, I'm not acting. The script has been written by actual events.