Admit it - this is something you've always wanted to say. And while there's a great deal of mystery surrounding the process of how to find an agent, it's relatively straightforward. This doesn't mean you'll be able to snap one up just like that, but the following tips will greatly increase your chances of success:
1. Think like an agent. Look at it this way - both you and book agents are essentially after the same thing: a book that sells well and makes lots of money for everyone involved. If you're a good writer with an interesting idea, the agent wants to make contact with you just as much as you want to make contact with him or her.
Submitting a well-written, attention-grabbing query letter is the best way to pique an agent's interest. If you can do that, you're already ahead of the game, because the agent sees right away that a) you know how to string a sentence together and b) you know how to hook a reader. These are two skills common to all successful authors, regardless of whether they write fiction or non-fiction.
Conversely, if you misspell the agent's name, bore him or her to tears, and announce in your letter that "My mom thinks this is a great idea for a book," you'll quickly brand yourself as someone who just doesn't get it - i.e., someone the agent will take a quick pass on.
2. Get yourself a platform. Agents get behind books not so much because they personally like them - which they generally do if they agree to represent them - but because they believe lots of other people will buy them. If you already have a following of some sort, such as a blog with several thousand readers, or a few published magazine articles, it's much easier to land an agent because you already have an established track record. It's not impossible to find an agent if you're unpublished and unknown, but it's harder.
3. Follow directions. People never want to hear this, but it's hugely important. You don't set yourself apart by using glittery ink, calling the agent at home, or sending your query letter wrapped around the jumbo-size Whitman's Sampler. You set yourself apart by the strength of your writing and your presentation - within the framework of what the agent wants.
I highly recommend Jeff Herman's Guide to Book Publishers, Editors, and Literary Agents. He gives you the skinny on which agents are looking for new clients, the types of books they're interested in representing, the types of books they're not interested in representing, and submission guidelines. (Some agents prefer email queries; some prefer hard copy queries. Some want you to send a few sample chapters right away, while others want only the query to start with. You get the idea.)