Magicians manipulate reality for their audiences -- or give the illusion of doing so -- reminding everyone that things aren't always what they seem. Magicians usually have several tricks up their sleeves, including choosing the right card from a deck and pulling a coin from behind a person's ear. One trick that often delights an audience is to make a person appear out of thin air. Of course, people don't really appear out of nowhere, but a magician knows how to make it appear that way.
Behind the curtain
Have someone hide behind a piece of furniture or wall in the background prior to the audience arriving.
Walk around the area in front of the audience, showing them that there is no one there.
Stepping to the front, slowly lift up a giant curtain. Hold it in place for a few seconds, allowing the person in hiding to run up behind the curtain.
Drop the curtain with a great flourish to reveal the person who, seemingly, appeared out of thin air.
Using a trapdoor
Place a rug on top of a trapdoor. The rug should be cut over the trapdoor so that a person can get through it. Then place a four-legged table on top of the rug. The table should also have a trap for a person to go through, as well as a lever for the platform to rest on. The entire platform should be connected via a pulley. This should be completed prior to the audience arriving.
Standing behind the table, the magician should throw a tablecloth over the table in front of the audience. It should look as though he is tossing it carelessly over the table, though he should make sure the cloth drops to the floor in the front.
The person hiding underneath the trap door should then be lifted as quickly and smoothly as possible up to a locked position under the table. The magician should then straighten the tablecloth so that the bottom legs can be seen.
Pull the tablecloth off the table. The person should simultaneously burst through the second trap door in the table and appear in front of the astonished audience.
When it comes to magic, practice makes perfect. The key to this trick is that the audience should never suspect the person was hiding there all along. This means that the person in hiding needs to be very fast and smooth to get in place in time. Practice in front of a mirror and in front of trusted friends who will give you feedback on how realistic the trick looks.