This is right up my alley. I was the manager for the online marketing team at Network Solutions and they are partners with Google, so I used to talk to people everyday about this.
I can't give you specific advise because each campaign is different and I don't know your goals/budget for this, but I can give you some advice and steer you to a couple of resources.
As a campaign AdWords is only going to be as effective as the work you're willing to put into it. It's not as simple as it seems and is easy to dismiss as not effective after a short time.
The first thing you should do is look at your competition. Search for the keywords someone looking for your service would and see what sites pop under the sponsored listings. Look at their sites and compare them to yours. Your potential customers will be doing that.
I see that you're in New York and doing a search for a New York magician brought up quite a few AdWords' results. You probably want to do some geo-targeting and localize your campaign. Target specific cities.
Next is what you really need to do is run several campaigns. One for general show, one that is holiday specific, another if you're targeting kid shows or corporate shows. By running multiple campaigns, it's easier to measure the effectiveness of the ad and the campaign.
Do keyword research and see what people are really looking for. Google provides a tool for that.
Coming back to your website, it can have an impact on the campaign. Google wants relevancy - be it in the natural/organic listings or in the AdWords. Google has a separate bot that looks at your ad, follows it to the site and scores it based on keyword relevancy. This can impact your position on the page and the cost per click. It used to be that the more you were willing to pay per click, the better your position is. This is not the case any more.
AdWords has an official blog worth reading: http://adwords.blogspot.com/
I would also recommend Search Engine Optimization for Dummies - it's a great book with an excellent chapter on Pay Per Click advertising.
Search Google for "AdWord Basics" and "adwords keyword relevancy" and that too will bring up some resources. Stay away from the sales sites that promise you everything with their system for only $97 (including bonus ebooks) - you know the kind of sites I'm talking about.
You should also be using Google Analytics to help track your site's traffic. This ties in perfectly with AdWords.
Let me know if you have any questions.