In this interactive video, Derren Brown makes you think of a card he wants. It works on most of the people.
Click to see Deren Brown perform "Card Suggestion" on www.youtube.com
He achieves this using suggestion. First, he asks you for a bright and vivid color, which is obviously red. Then he makes a diamond-like shape with his hands, suggesting a diamond. When he talks about numbers, he is drawing the shape of 3 in the air constantly and even makes three sounds (bum, bum, bum) as he mentions the 'things down the middle'.
He makes all this gestures so quick you don't actually notice them the first time you see the video, but it is enough to make a majority of people think of the three of diamonds. You can try it out on other people and see if it works on them, just don't make it too obvious that you're trying to influence them.