Common Gerber Mistakes to Avoid

Missing board outline layer — fab shops cannot quote or produce without it
Solder mask clearance set to zero — all pads will be covered
Drill file units mismatch (metric vs. imperial) — verify with your EDA export settings
Aperture macros not included — some older Gerber viewers/importers require explicit aperture definitions
Silkscreen artwork crossing into pads — causes inspection issues and may short
Multiple board outlines in separate files — consolidate all outlines in one layer