Contact publishers who won't charge you. Many advertisements on websites such as Craigslist will offer to publish your work for a small fee. A real publisher, whether it be a book or online publisher, will never make you pay to have your own work edited and published.
Research the publisher if you've never heard of the company before. Just because you don't know a company doesn't necessarily mean that you're being scammed. Look up the name and see what work has been published by the company. If you find that no books have been published, you've probably encountered a scam.
Speak to a person who works for the company before you send the company your work. Most book publishing scams found on the Internet will ask you to email them your work. Send an email in which you ask for a phone number. Explain to the person that you have a few questions and want to have a conversation. If they insist that you send them your work first, steer clear. They may be trying to steal your work so that they can pass it off as their own.
Look for the company name on the Preditors and Editors website. This website lists numerous known publishing scams. Click on the “Warnings” link near the bottom of the page to see a list of these scams. You can also use this website for more information about book publishing scams in general (see Resources below).
Ignore publishers who advertise that they need writers. Real book publishers don't place advertisements on Craigslist or writing websites. They don't have to. Most of the time, legitimate publishers will have an overabundance of work submitted to them.