Who are you going to call? Before you go reaching for those yellow pages and calling one number after another, let's narrow this down a bit.
You could reach for the yellow pages, magazines or your local newspaper's classified section - but in this age of technology, it's much easier to search the world wide web (after all, that is how you found this page). The web can present much more in-depth information than a simple ad can present and might even give you a chance to get to know how the performer thinks about his/her craft and audiences.
Party planners, entertainment bureaus and agencies can be found in most cities. A good thing about using agencies is that they specialize in hiring entertainment and will almost always be able to find you an entertainer for your event. Someone will definitely show up and everything should run very smoothly and professionally. The down side to using agencies is that many party-planning bureaus will send you just a "generic entertainer" who may be good, but will not always be top-quality.
There are, of course, exceptions, as some agents allow you to book a performer by name or provide you with information about the performer whom you might select. For better or worse, these agents will normally have a higher fee than others for this service. Generally speaking, an entertainer will cost you more if you go through an agency than if you book them directly. Just be aware that entertainers and agents work on a first-come, first-serve basis. So, if you know what you want, it would do you well to inquire as to the availability as soon as possible. Note: some people book entertainers several months and even up to a year or more in advance of the event. However, inquiries made at least one month before the date of the event should still present a decent list of entertainers from which a selection can be made.
In this business, experience is the key. A knowledgeable performer and / or agency will listen to your needs, wants, and desires and be honest about what they can and are unable to do for you in regards to what you desire. The down side to direct booking is that there can be a bit of a questionable feeling if the person is really professional. This should not be a major concern for you since most professional entertainers are just as (if not more) professional than many party planners. There is, of course, a small risk of running into an unprofessional or inexperienced entertainer, but the information he/she presents about him/herself, what information they ask from you in relation to the event and the feeling you get when you speak to them, or their staff, can often squelch any concerns.