How to create a art file on a computer for a commercial printer?

Answer 1

Use real software.
Such as Quark or InDesign for the layout.
Use Illustrator and Photoshop for the images.

Dont use software like Publisher, Word, Excel, or Powerpoint.
Some printers might not take them (we do), but we charge extra, cause they are not easy to work with.
Word, Excel, and Powerpoint doesnt know CMYK from RGB, from PMS.

Also stay away from the design programs you can buy at Walmart for $10.
They are worthless to commercial printers. And will cause you headaches when you show up with your file, and they laugh at you.