Dave's horror story about watching his case come plummeting down the slide nut-end-first reminded me of this pointer I've read before, either in some past thread here or at the wonderful site www.frets.com.

Pack the top end of your guitar inside the case with whatever you can --wadded newspaper, foam rubber, strofoam, etc. Just make it tight and fill the space (the entire space above the pick-box) completely. This area is where the guitar is most vulnerable to shock, where it can be most easily damaged by blows that do not penetrate the case.