Originally Posted by Martian

I have psychic powers. Or at least, I can convince people I do.

There is an ability called cold reading. It basically relies on common circumstances and human nature. It's all about observing an individual (who need not be present - tone of voice can tell a good cold reader just as much as body language) and using your observations to make educated guesses. The particularly skilled are able to adjust their readings on the fly and therefore turn misses into hits, but even when you bomb out you can just depend on the Barnum effect to carry the illusion.

Some cold readers start out as cold readers and gradually convince themselves that they have some sort of special ability; this too is human nature. Some folk are just naturally gifted at the art; their cold reading takes the form of 'gut feelings'; they don't know how they know something, they just know that they do. This is commonly attributed to some form of paranormal ability.

I'm not saying psychics don't exist or that it's not possible, so all those people who want to say 'but what about...?' can go ahead. I just happen to be skeptical and have yet to see anything that convinces me.