The Right Magician For The Right Event: There are different kinds of magic and magic shows. Some magicians only specialize in one area, others in a few. If a magician specializes in a magic show for kids than you may want to rethink that his/her material will be good for adult entertainment.
When choosing a magician find out how many years experience he or she has, what kind of tricks can he/she do, does he/she have references for a similar event that you are running and does he/she have a promotional video of his work in action.
Here are a few types of magic shows: Comedy Magic is more focused on the laughter aspect rather than the magic itself. Possibly more audience participation and incorporation of monologue or jokes can be expected. All magic shows may have some elements of comedy however, a Comedy Magic Show adds zaniness and laughter.
Silent Comedy: May involve miming, or other non-verbal forms of entertainment with magic tricks. It's basically comedy without speaking. Great for crowds with many different ethnic groups, where everyone speaks a different language.
Children's Magic is great for birthday parties, live events, fund-raisers, street festivals and more. The magician will perform tricks especially designed for kids. Keep in mind the age group of the kids. Children between 4 and 6 will appreciate different magic tricks than 10 or 15 year olds. If there are many ages present then you should discuss this with your magician so that there can be a greater and more varied selection of tricks.
A Stage Show Illusion is referred to as a larger show usually for larger audiences. These kinds of shows have more elaborate stage settings and dynamic illusions...like David Copperfield. I'm sure he's available to perform the night of your birthday party, if you can match his asking price!. Actually a much smaller version of this kind of magic is what you probably can afford. This is known as parlor magic. Parlor magic is designed for smaller audiences and caters well to in-home parties.
Walk-Around Magic:A very exciting form of magic because it is done up close, right before your eyes, underneath your nose. This type of magic is not designed for stage but more for trade shows, grand openings, corporate events, birthdays and weddings.
Keep in mind, in most cases you get what you pay for. Check out the magicians promotional material, videos and references. There is usually a great difference between a $100 magician and a $1500 one.