After five years and almost one thousand projects, give it or take, I believe I have come up with a handful of more or less reliable signs that you're dealing with a bad client. I haven't reinvented the wheel, that's for sure. It's just like in that saying. Maybe I don't know what I want, but I certainly know what I don't want. The same goes here. Maybe I don't know how to find a good client, but I certainly know how to avoid a bad one. Also, I'm far from an ideal list. Sharing experiences regarding bad clients can help a lot. After all, we play in the same team. In addition, I strongly believe in Good Karma principle. Meaning, there's plenty of room and clients for everybody.
Deal with real people not with avatars