When selecting printing paper, you must prioritize Grammage (GSM), which determines the paper's weight and thickness; for standard office use, 70-80 GSM is typical, while premium brochures require 120-250 GSM. Additionally, evaluate Whiteness and Brightness levels (CIE measure), as higher brightness (above 160 CIE) ensures sharper color contrast. Don't overlook Opacity, especially for double-sided printing, to prevent 'show-through' issues. For high-speed digital printing, ensure the paper has low dust content and anti-curl properties to prevent machine jams.