Ah, the smell of fresh ink. This is where the two worlds of digital and print meet. REALLY meet. Assuming the files have been produced in the appropriate manner, and assuming you meet the specs of the printer for this project/product (CMYK? 300 DPI? x1-A PDF?) it is time to move on to the down and dirty specs. Is the paper stock what you require? Is there UV coating? Aquas? Sixth color printing? Digital or Offset? Does your material clear the gutter and crop? Is this something you need to address on the fly? While all of this should be addressed by the time the materials arrive at the printer, it is imperative to know what to expect of your printer and what your printer expects of you.