Alright, from now on, the first question I ask any potential housemate is: which of the following disorders do you have if any? Schitz (that guy), histrionic personality disorder (the previous one), sociopathy or narcassism? If they answer yes to any they can fuck off.
On a more serious note, I'm not sure I can ask that directly, but I'll be attempting to train myself to look for those traits.
Also, while we're doing amusing share household anecdotes, the previous housemate seemed decent at first, then never did any housework(normalish) and then decided to move out cos we caught her boyfriend stealing from us and we said he wasn't allowed around anymore. Apparently that was totally unreasonable and I should've thought about how that would affect their relationship(not a very fucking normal reaction)...