My formal training was in graphic design. The production part wasn’t a big part of the curriculum. If you were lucky, like I was, my first two jobs were at design studios where I learned about printing and typography. The best advice I gleaned was: make the printer CSRs your friend. Talk to them EARLY on in the design process, tell them what you are thinking, and ask them for tips on the best paper to spec, finished sizes, etc. The good ones will help you, them, and your client, look good.