I remember when Photoshop fit on a floppy disk. That might date me, but it gives you an idea of how much experience I have in print production and graphic design. By starting out in the journalism field and then migrating to the printing world, I certainly got the full spectrum of what to publish and then how to publish. Just because it looks great on your screen doesn't mean when the ink hits the paper you are going to be happy.
Giving your image and layout files a good look over will ensure that problems on press will be a thing of the past.