There's a good South Park episode to watch that points and laughs at the occult, which manages to explain how they're actually done. They're like magic tricks, except they use their language, a wee bit of chance and people's emotions. I'm sure Houdini didn't manage to do the things he appeared to do, it wasn't magic, they were illusions - playing with your eyes, things like tarot cards are no different, they play with your mind instead.
We did our own Tarot card experiment - we had different readings done, sounded very appealing, meaningful and sounds like something that would happen. Then we compared readings and most of them tied together and made sense to each individual. Then I decided to read all of the answers in the tarot book and about 80-90% appealed to me.
It's the beauty and horror of language, using the right words in the right place can have any effect on a person's view or belief - read a tabloid newspaper and you will see how they utilise language in order to have the effect they want. Use of ambiguity in the right way can make anything apply to anyone.
If you get a reading like:
"In the next week you'll have struggles to over come, be strong and persist, you will reach your goal." (I made this up by the way)
Me handing in CVs next week.
Take it to last week (for this week), I had to look for job applications and a student loan form to sort out.
Take it a week before, I had to prepare my flat in halls to leave and hand my key in - involving tidying up my room.
The week before - elections for the Student Union Officers, I was running (And got my position)
All struggles and things I felt reluctant to do and had to persist and managed to break through and get those 'struggles' out of the way - if you got this in a Tarot Card, you may think "that's true!"
You can say one thing and leave the other person to interpret it and put it into context for you - the brilliance of the English Language.
If I got a Tarot that said:
"Don't worry about filling out your forms, they're not as daunting as they may seem, by the end of the week you'll be done, look forward to that." Then I'd consider them otherwise.
There's a lot of ways you can 'experiment' to prove against Tarot, heck try reading someone and use my 'struggle' example.
"Experience never provides its judgments with true or strict universality; but only (through induction) with assumed and comparative universality." - Immanuel Kant