The main warning I can give is basically making sure he camera is wound on before changing the lens or mounting a lens.

Its also important that you align the film arrow with the arrow and arrow on the film back and not have film slack. That will result in uneven spacing between frames.

I'm by no means a Hasselblad geek, I just love using mine. I highly recommend you join Hasselblad User Group mailing list, see instruction at the bottom of this page http://www.kelvin.net/Hasselblad/guidelines.txt

And also buy some of the Hasselblad books, you dont need the latest editions for the 500cm so they can be had cheaply on ebay.

Have you an exposure meter?