…and then there’s agents.
This article by an agent makes a very good point: you don’t want just anyone mucking about with your livelihood. Just as you would check out someone who’s going to do brain surgery on you or deliver your baby, you should check out the qualifications of a literary agent. Why?
Well, go read the article (including the links she gives off of it) then if you still don’t understand come on back and we can talk about it.
One thing that checking up on someone you are taking on as a business partner (which is what an agent is…if you don’t win, they don’t either) is that it makes you look more professional. Approaching someone and not knowing what they prefer to work on wastes both of your time. Besides, if you find that they sell what you write, it’s much more likely that they’ll be enthusiastic about working with you. And if you love the books they have sold, you’ll be enthusiastic about working with them too.