I posted some of this as a comment over at Pubrants , but I want to mention it here as well.
A loser agent is worse than no agent.
I'm not talking about bad agents here, the evil predators who want your money and are just a scam in disguise. I'm talking about the agent who would really love to sell your book - but just because she calls herself a literary agent doesn't mean she is one.
Rachel Vader, an agent with Folio Literary Management, talks a little bit about it here. Your agent needs to be legit. I admit that I can't give you a tremendous amount of intel about what goes on at a literary agency, having never worked at one, but I can tell you some things from an editorial perspective.
Your agent needs to know editors. She needs to know what editors are looking for. She needs to have a relationship with them. She needs to have made previous sales that are decent enough so that when she calls up my boss and says, "I have a YA vampire novel that I think is just up your alley" he will take her seriously and ask her to send it over and have me read it. Because he trusts her judgment and knows that she doesn't usually waste his (or my) time. She needs to be a decent negotiator. When we send her your contracts, she is the one who looks it over and tries to get the best deal for you. I'm not going to lie to you - when we write our contracts, we're trying to get the best deal for the publishing house. We want to be fair to you, no question, but we want to get the most we can. Your agent has to be the advocate who speaks fluent contractese (and believe me, it is a language all of its own) and translates that into how much money and subsidiary rights she can get for you.
That's only a fraction of what your agent needs to be able to do for you.
There are loser agents who troll for naive and eager newbie writers. They show up at SCBWI conferences and give you their card and enthusiastically praise your writing, and bam! you have an agent. They do this not because they are trying to scam you, but because they are loser agents, and they want to build their author base, and they figure, if they sign up enough of you, one of you might make it to the big time for them. What they neglect to tell you is that for all the good they can do for you, you might as well be making it to the big time on your own. They are desperate for new talent, but they can't provide the support and backing that your novel deserves. Loser agents can't do any of the aforementioned things that an agent should be doing for you. They don't have the experience, the contacts, the know-how.
(If you're wondering how anyone gets all experience and know-how to get started in the first place, the answer is, of course, by starting as a junior/assistant lit agent and working their way up. Not by putting out the welcome mat and shiny window sign declaring themselves to be an agent.)
I hate the loser agents sometimes more than I hate the evil agents (okay, I hate them, too.) But loser agents are just not fair to you. You wrote a book. You put your sweat and blood and time and energy into it. And then an agent signs you, and you get all excited, thinking that the horrible submissions process is finally over (on your side, anyway.) Only, your agent is a loser, and instead of spending the energy to find an agent who will actually take your book where it can shine, you're in the hands of someone with as many publishing connections as you have. They're not doing anything illegal. But it's still not fair to dupe you like that.
Reading the slush pile, when I hit on a query letter from a so-called "agent," I always have to fight the urge to track down the author's contact info and send them a letter telling them to drop their loser agent like a hot potato. An agent who submits to slush is worse than no agent at all. If you submit to slush by yourself, you have a 1 in 50billion chance of catching my interest. If your agent submits to the slush, as soon as I see that it's a loser agent, it goes in the trash. Seriously. You can submit to the slush pile yourself. You don't need an agent to do that for you. It doesn't make you look good - it just makes you look duped.
I once did some freelance work for a literary agent. The MSs weren't very good, but I did the best I could to give them constructive critique. Afterwards, the agent said to me, "I've never submitted a children's book before - do you have any tips for me?" It threw up every red flag that I had. Even though she was a paying customer, I never did any more work for her. It just felt wrong.