Litter-vention?

I know that you all know how awful it can be when a house cat is not using the litter box.  I also know that you have ALL read my blog archives and already know that there can a medical cause for this behavior that MUST be addressed before resolution can be expected. :)
But did you know that your choice of litter can also play a role?  Some cats have a very specific substrate preference, so if your cat is not using his/her box, you can certainly try another brand, type or scent.  Since the guidelines say that you should have a litter box per cat + one more, you should have multiple boxes to try different things.   You will need to be vigilant, maybe even keeping a written log to document your cat's preferences or lack thereof.  Don't just make decisions on your impressions. Try to be exact and let your cat tell you the litter-vention facts!