Be nice to your agent.
My boss acknowledges that a lot of writers, particularly career ones, are inherently weirdos. She doesn't outright say it, but when writers are unreliable or obsessive or can't seem to grasp the world beyond their work, she's not surprised. I'm not surprised; I was a weirdo growing up and I'm a weirdo now. My publication record is just confirmation of my right to be one. That said, it's important to maintain a professional working relationship with the people around you, and in this case, your agent or potential agent.
There's been a few cases over the years I've known her where my boss has declined a potential client, or cut lose a former one, because of their behavior. Mostly the former, but there was even a case where a potential client came in with an offer from a publishing company with a huge advance attached to it. In other words, free money for my boss, whose job becomes to look over the contract and pretty much nothing else, and then receive a significant check for her work. Agents love these clients. That was actually how I got my agent; various agents were considering my work and at the same time I landed an offer from a company after I pitched to the editor at the BEA and I called around to the agents considering me, said I had an offer on the table, and waited for them to call me back. Within the first 24 hours, three did. Another begged for an additional 24 hours to read the manuscript, and a fourth was vacation and still asked about it when they got back 2 weeks later. One person did say "OK, I read it, I'm legitimately not interested" but otherwise I had my pick. It's a pretty awesome position to be in.
Back to my boss. She got this offer, which really a lot of money already on the table, and she was still debating it when I last spoke to her. The author, when she spoke to him, was pushy and demanded things of her like lowering her industry fees (which is not a negotiable topic), made comments critical of her other clients, and didn't get back to her when she emailed him basic questions that would be crucial to the agent/client relationship. It really came down to "Do I really want to work with this guy?" Knowing her, in the long run, the answer will probably be no.
So if you're working with your agent, or trying to get one, be polite. Promptly answer emails if you're available to do so. Don't ignore questions. In short, don't be a douche. We don't like working with them.