When I was in Minnesota week before last, I made an appointment to meet with Laurie Harper, a nonfiction agent with whom I had worked a few years ago. She's been in the business 22 years, really knows her stuff, and is always a blast to talk to.
Laurie became an agent because she was a publisher of gift books and wanted to close down that business. She wanted to find other publishers to take on the books she could no longer do, and found out she liked agenting a lot. So she stuck with it, and moved her business from San Francisco to St. Paul when her personal situation dictated it.
So here's what Laurie has to say about what an agent does and how to get into the business:
An agent represents an author, presenting the author's Work (proposals or completed manuscripts) to select publishing house editors who are a match for that author, to secure a publishing deal [contract] for the author. This often involves first developing the proposal or book idea with the author a little bit to make it ready for publishers to see. Once there is a publisher's offer to publish the book (which can take between 2 months and a year), the agent negotiates the publishing contract on behalf of the author; often handles some of the subsidiary rights licensing for the author (like foreign translation or a film deal); receives and manages the author's money from publisher(s) and verifies the royalty statements; advises the author on all publishing matters such as next books to write, copyright questions, permissions questions, issues with the editor, general marketing questions, etc. The agent does not personally manage
the author's publicity (which is done by a publicist) [either a freelance publicist hired by the author or the publisher's staff publicist].
The author-agent relationship can be structured book-by-book, or--as is more common--developed over years as they work on multiple projects together. It's often referred to as being like a marriage. It is a very personal relationship. So there are skirmishes and divorces, and then there are long-term ones that flourish. You'll see it all. The idea is that the author is an expert in his/her field of writing and the market/audience, while the agent is the publishing business expert. If they put their heads together and combine those talents, author and agent win. The agent is commissioned on the author's income (usually 15%) so they are vested partners--win, lose, or draw. The agent must quickly learn to make "good bets" on which writers to select and work for because you can do a lot of work and never get paid...It's a gamble.
For anyone wanting to become an agent, there is no better way than to work in an established agency as an assistant (or intern) for at least 6 months to one year. You will see the range of work done and the variety of skills that an agent needs to develop. You will see the kind of publishing instinct it takes, and the ability to build good relationships with both authors and editors. There are few actual classes about agenting, though Peter Rubin in NY offers one through his agency. Many of us learned by doing, and by reading books like How to Be Your Own Literary Agent and Negotiating a Book Contract and How to Sell, Then Write Your Nonfiction Book (or Fiction Book") -- kind of books. We read what is there for the writers to represent themselves and we read what lawyers publish about it, and we read in writers' magazines what both sides have to say about the agent (who is in the middle) and in all of that, you figure it out. You go meet with editors and chat about book projects you are representing, and off you go...
Most agents come to this profession by accident--they were doing something else but felt a commitment to get a certain author published, and the next thing you know, you're representing more authors and pretty soon it's a full-time thing. It grows rather rapidly because there are so many authors and not enough agents to take everyone. But there is also a turnover in agents because it's hard to make enough money on commission only.