I have never been to a psychic or anything, but one guy I saw on tv was quite convincing. Not the usual type, as he found a system to prove the veracity of what he was doing. A guy who painted his dreams and saw that some of them coralated with later events.
He would take a photo of himself with the paintings in his local bank under the bank's date and clock showing, to prove when he was standing there with the painting.
He had paintings that matched up with the 9/11 attacks, the murderer Thomas Hamilton who shot a bunch of kids in a school in Scotland, and a serial killer, Fred West, who hanged himself.
It was called 'The man who paints the future' and was on ch5 on uk tv.
I couldn't find the doc on the net but found this interview with someone who exposes fraudulent psychics and she says that this guy 'certainly warrented further investigation.'
http://www.badpsychics.co.uk/thefraudfiles/modules/sections/index.php?op=viewarticle&artid=54
The only thing they said was that maybe he added details to the pictures after taking the photos, but I seem to recall that they magnified the pics and saw details there already. Some of the details were amazing, like a photograph of the murderer Thomas Hamilton posing with his scout troupe that was later released into the press after his murders.