Let's say someone is wrote down the name Robert on a piece of paper and stuck it in their pocket. They are told to think of that person. You ask them "The person you are thinking of has a nickname or go by a shortened version of his name? They answer "yes." You say, "That is what I thought, I'm getting the sense that their name is Rob or Bob." That enhances the effect because you aren't revealing what they wrote down, but something beyond that (i.e. they don't go by Robert but like to be called Rob).
If they pick the 8 of Hearts and you tell them their card is 9 of Diamonds... not so much.
Another technique is to correct yourself before the reveal. if they are thinking of their zip code and it is 90210, you first write 60201 and then correct the 6 to a 9 ("I sense one of the numbers is backwards") and then switch the 01 to 10 (and that I've got something reversed). That would strengthen the effect because you show it is a process and that you are doing something further by sensing that your answer isn't exactly correct.
A better technique is using a more detailed reveal. Let's say they are thinking of having spaghetti and meatballs. You ask them to imagine the scene. You mention thatthere is a checkered red table cloth, a cheese shaker on the table, there is another bottle on the table... perhaps a Chainti?; the waiter has a sleight european accent.. You tell them that they pick up the menu and there is a lot of choices of fancy dishes, but they are going for something simple. Spaghetti with a meat sauce? Then you say "Wat no, you are imagining a huge bowl of spaghetti with meatballs the size of baseballs -- are you thinking of spaghetti and meatballs?" There are ways to fine tune your description - a simple "You're not thinking of one of those fancy restaurants, are you?" at the beginning can dictate whether you describe the local italian place or the fancy restaurant in the big city.
The "too perfect theory" may apply here, although it is often misrepresented and I might be adding to that confusion.
Don't go there... that's another thread altogether.
