I present workshops for those who'd like to publish, and I'm constantly surprised at both the naivete of writers and the gall of scammers. Here are a few things I would avoid as a pre-published author:
An agent who charges a fee. There are LOTS of agents around, and the good ones don't charge except (maybe) for mailing. My experience with this was tough to take. I was so excited when an agent wrote and said she loved my characters and thought I had real promise. Then at the bottom of the letter was the fee she would charge up-front to represent my work. I knew enough to go to Preditors and Editors, and there I found NOT RECOMMENDED by the agency's name. These people take your money and throw your MS in a corner.
An agent who recommends that you "spiff up" your MS by sending it to an editor he/she recommends. They're in cahoots, and you'll pay through the nose for editing you could get somewhere else for less. A variation on this is a plug for you to buy their book, which promises to tell you everything you need to know to get published. You can find out what you need to know free on the Net (like right here, for example).
Websites who offer to copyright your book for only a few hundred dollars. You can do it yourself: a simple form on the US Govt website. I think I paid $20.00. Be aware, too, that you don't need to copyright. It's yours as soon as you write it down. You also don't need to mail it to yourself or any of that other stuff. It's yours. And BTW, don't worry about an agent stealing your work. Good ones won't, and bad ones have easier ways to make money (see above).
A subsidy company. I know, there are subsidy publishers who give a square deal, and there are people who have self-published and done well. Still, you need to be aware of two things: first those authors who do really well are few and far between, and second, you'll do a huge share of the work. Better companies hold your hand, send you a packet of info to get you started, and help with cover and editing, but you will pay for all of that. Then you'll pay for the books, and then you'll have to go out and sell them yourself. Even if they offer a quality product (and be careful to find out who does and does not do that) they give no guarantee that you'll make money. That's totally up to you.
The reason these types of scammers survive is because we all want to believe in our work, and we all think if it could just get "out there" it would sell. We often rush things in our eagerness to be published, and as one woman told me just last week, "I've decided I will have to pay, so I'll pay." Better, I advised her, to invest in an editor you know will do the job, a well-educated acquaintance or a recommended professional. Better to let someone else (a reputable agent or publisher) judge if the work is ready. Better to save your money for real promotion when the work is legitimately published.
People in my workshops often admit that they self-published too soon and now see that the material wasn't ready. Judging from examples they've shown me, I can only attest to the truth of that statement. But those who prey on authors will tell you they can publish your book six weeks from today. One of them may be advertised to the right of this message. Think hard before you click on that ad.