How to Detect a Toxic Customer (2010)
Never say no.  EVER.  I mean it.  Not one single time, not under any circumstances ever.  Make them say no.  The way you do this is by determining just how much you would have to be paid in order to deal with the customer.  It doesn't matter if it's a completely unreasonable number.  Name it.  Don't just presume they will refuse and turn them away.  Tell them that your product which would normally cost $1k is going to cost them $50k or $100k. What have you got to lose?  Worst case scenario they will pay you a giant amount of money, and you'll have a bit of a headache, but one that you have already determined you are willing to take on for the price you named.This applies to customers, potential employers, and basically everything in life.  There is ALWAYS a price.  So take the gamble.  Let them decide if it's worth it from their own perspective... maybe you'll get lucky!