A couple years ago I posted an article on my blog that made the rounds a bit, titled "Writers and Other Delusional People." It offered a number of useful truths I'd discovered over the years about the business of writing. Looking back, it's still a pretty good post.
However, I made a comment afterward mentioning my then-agent, now my ex-agent. Yes, through the school of hard knocks, I have since learned some more lessons that I will pass along to you. Check out my original post, then skip down through the comments to find my Rules of Agents.
Actually, let me make it easier for you. I'll go back and append the list (and setup) to the original "Writers and Other Delusional People" post.
Find it here.