For writers there are sites that aim to put the light on shady behaviours such as Absolute Write, Editors and Predators, and Writers Beware. However, sometimes issues don't come to out of the shadows until after people have been burnt. There's no smoke to warn them of the impending fire.
Here's some things to look for if you can't find anything ominous on any "warning" sites:
- Research their credentials: If they haven't gone through a agentry internship then steer clear. They should also have done their time as a junior agent.
- Research their sales: If they're not a recently promoted to junior agent, they should have sales. Check out who they're selling too. Are they selling to publishers you can see your book with? Are there any sales with advances? If they're a junior agent with no sales yet, what are the sales like for the agency as a whole.
- What's their presence online like? Do they talk in the correct publishing terms? If they have no online presence at all then are they the right agent for you?
- Research the owner: If they don't have SIGNIFICANT experience (like years and years) at a SENIOR level in the publishing industry don't sign.
- Research the editors: They too should have significant experience in the publishing industry - not freelancing.
- Research their authors: See if anyone was signed with them then suddenly is with someone else or has self published.