Create/output the PDF or AI as a high resolution and high quality file. Make sure that all graphics are either grayscale or CMYK images. Make sure that black type is really black and not made up of RGB or CMYK. If the document contains drop shadows or uses transparency, then it the file needs to be “flattened”. Our Prepress Department can work with you and explain how to do that. It is unnecessary to use trim marks or a color bar when outputting the file, just make sure if the document bleeds, make sure there are bleeds in the file.