I'm a sucker for optimism.  I'm also full of myself when it comes to making judgment in taking on clients. 

I've had referrals of very good clients from high-maintenance ones and vice versa.  My policy is to interview all client referrals.  The initial phone call will determine whether there is a mutual match, which - as I would disclose to the referee - would be the sole criterion whether to extend my conversation beyond the courtesy initial interview.  There were interviews from which I ran to the hills within a few minutes.

It's also a matter of preparation (check list) for the interview.

Just my 1.6 cents.  (Was 2 cents before the recent NASDAQ fiasco.)