People often ask me which blogs I read, just as they used to ask my favorite marketing books.  I read a LOT of blogs, but these come to mind first (and, since I subscribe to many of them, they come to my inbox almost daily):

Every bad client that is now wasting your time, failing to produce results or missing payments was once a prospect that you chose to accept.  Did you ignore early warning signs or intuition that foreshadowed the future, rotten outcome?