How does one go about finding an agent?

There are many excellent online sources that will guide you through the process of finding an agent. Why do you need an agent? These days editors of commercial publishing houses will only consider for publication work that arrives on their desk via an established literary agent. This is the main reason why you need an agent; agents have become the sentries at the doors of the publisher and, in so doing, have gained an incredible amount of power in the industry. Agents are business people who like to read. They are not editors. A few publishing houses still accept unsolicited manuscripts and you can always approach an independent press without an agent. Having an agent makes life easier and increases the chances of your book's success. An agent takes %15 of everything your book earns. Here are the sources I recommend you turn to for more info on the subject:
www.pw.org
www.agentquery.com
www.absolutewrite.com