Okay, so I'm going to combine a couple of the questions, because they're both about agents:
How important is it to acquire an agent? Do we dare submit on our own?
What are the differences (benefits, drawbacks) between querying an editor versus querying an agent, and should it be handled differently by we authors?,
Getting an agent, especially at the beginning of your writing career, isn't always a matter of choice. If you are going to submit to certain lines or certain publishers, you have to have an agent, as they won't look at "unagented submissions". (It is sometimes possible to get around this by meeting the editor, maybe at a writing conference, but their first question is often, "Who's your agent?") The big NY publishers tend to use agents as first readers or "gatekeepers," winnowing out the worst manuscripts. So if you've got a book bound for the publishers, you might have to get an agent whether you want to or not.
On the other hand, a lot of agents have taken to saying they are only open to currently contracted authors. (Anyone gotten the infamous rejection: "Love the book! Write to me when you've sold it, and then I'll represent you?") So if you WANT an agent, you might not get the one you want until after that first contract.
Do you need an agent? Well, think about what you want from an agent. If you just want a quick sale, you might decide to go it alone, if you're submitting to an editor who will read unagented material. But if you want more than the standard advance, or a better than standard contract, you might look for an agent first. Certainly there are certain types of "high-concept" books that a good agent can do wonders with—getting a great contract, reserving film rights, selling the film option to
However… notice I keep saying "a good agent." A good agent is worth his/her weight in gold (sometimes literally— I suspect JK Rowling would NOT be a billionaire if she hadn't had a good agent), but a bad agent is worse than no agent at all. Get a bunch of published authors together in a bar (so you can get them drunk) and ask them for their bad agent stories, and you'll hear things that will curl your hair-- embezzling agents and editor-antagonizing agents and negligent agents and cheating agents and so on. So don't think about getting "an agent," think about getting "a good agent," if you decide you need one. And remember, the prime purpose of an agent is to sell the book and negotiate the contract, not to make you feel good. I know too many writers who look at getting an agent as an end in itself, when there's another very big step after that (the agent getting you a contract). Focus on that, and find the agent who can help you most.
Once you've got a contract, however, you might decide your needs change—you need more long-term attention, beyond this single book. Agents should be focused on your career and not just this one book, so a good long conversation about what sort of books you want to write and what sort of career you want to have should happen early rather than late. There are good agents who simply aren't the right match for a particular writer. Let's say you want to keep your day job and write part-time, and the agent wants you to sell (and write) three books a year. Or maybe you want to sell big thrillers, and the agents thinks you should play it safe and continue working on those little cozy mysteries. Or you love what you write, and the agent loves your voice, but thinks you should be writing something else. These agents might all be great for someone else, but they probably aren't right for you, because their vision of your career is different from yours.
As to queries, it's a matter of focus. The editor is probably buying single books, while an agent is looking for an author. So the query to the editor should focus on the book, with maybe a paragraph at the end telling what's relevant about you (you're an attorney and this is a legal thriller, for example, or you think you will do a great job promoting this book because you have so many contacts in the community). The query to the agent should introduce the book, but spend maybe more time introducing you as an author—why you are likely to be successful, what your career plans are, what writing successes you have had in the past. If the editor likes your book, who you are won't make much difference (in the main… obviously if you're a
So… just keep that in mind. Both types of queries should deal with your book and you the author; however, the editor-query generally focuses more on the book, and the agent-query focuses more on you. For example, I'd be sure, in an agent-query, to mention that I'm good at marketing and promotion, that I speak to a dozen women's groups a year and can hand-sell books then, that I can get blurbs from NYT-list friends (I'm making all that up, alas!). Those are items of interest that the agent knows she can use when she pitches your book to an editor.
This is why meeting with an agent at a conference is usually more productive than meeting with an editor. An agent can pretty much decide to take you on right then, but an editor isn't going to be much swayed by your sterling credentials and great charm—he'll say, "Send me the manuscript," and make his decision solely on whether the book works for him and fits his line.
By the way, I'm hearing more and more that agents often ask you to get a blurb (a recommendation) from a prominent author if you can—before submission. This is one more selling tool the agent can use. However, most new writers don't have access to a lot of prominent authors, and even if they do, many are resistant to asking for that sort of favor. But that's something to keep in mind. For example, if you're workshopping the book in a class with a well-known author, you might think about asking for a read and a rec. That blurb can actually go with your submission, whether it's to an editor or agent.