The magician gets out a business card, holds it in one hand, and announces that a prediction is going to be made. The magician writes something on the card and then holds it with the writing toward the floor so that nobody can read what was written.
A spectator is then asked for a piece of information (name, birthdate, phone number, gender) unknown to the magician. The magician then hands the business card to the spectator. The prediction written on the card matches the secret piece of information.
There are as many ways to do this trick as there are positive integers less than three.
One method, the one favored by less adventurous magicians, involves asking only questions that the magician already knows the answer to. Safe items to ask for might be the spectator's name (if the spectator is known to the magician), the color of the spectator's shirt, or the day of the week. When the time comes for the magician to write the prediction, the already-known "secret" is written. If this is done, it is important for the magician to remember to ask the spectator a question that will have the written item as its answer (for example, if the magician knows the spectator's hair color, the question should be, "What color is your hair?" not "What's that thing on your lip?")
Another method is more flexible but takes a little more skill. The magician only pretends to write the prediction before the question is asked. Instead, when the spectator has revealed the answer, the magician talks for a minute about telepathy and minds meeting through the aether and the science of the supernatural and maybe a bit about baseball, all the while "doodling absently " on the card with a pencil. In reality, the magician is not doodling at all but writing down the just-revealed secret. The misdirection of the sparkling conversation misdirects the audience from the prediction and gives the magician plenty of time to write while the heat is off.
Note: Care must be taken with method number two. If the magician writes too quickly and doesn't watch the pencil, the prediction will look like it was written by someone who was all thumbs and may not be legible. For best results, the magician must use one hand to hold the card and one hand to write while keeping both eyes on the card. Some magicians find it hard to talk and write at the same time, but a little practice (and perhaps some minor surgery) generally clears this right up.