Set up the file for print
Use a PDF where possible. Add 3 mm of bleed on every edge and keep important text at least 5 mm inside the trim.
Check resolution at final size
For close-up items such as cards and brochures, aim for 300 dpi at the printed size. Large banners viewed from a distance can be lower, but send the largest file you have.
Convert text to outlines
Outline fonts or embed them in the PDF so nothing is replaced when the file is opened on our side.
Expect colour to shift slightly
Screens use RGB and printers use CMYK. Bright screen blues and greens print duller. A proof shows you the real result before the full run.