Artwork should be provided at 300dpi where possible (150dpi OK for large format items), with 3mm bleed and crop marks. 20mm bleed required on outdoor banners.
Allow 4-8mm "safe zone" from the edge for any text / important images.
CMYK files preferred. Any RGB or Spot colours may produce unpredictable colour results. Fonts to be outlined and transparencies flattened where possible.