1. Maintain High Contrast
Always use a dark foreground on a light background. Inverting these colors can make codes un-scannable for many older devices.
2. Size Matters
For print materials, never go smaller than 2cm x 2cm. If the scanning distance is large (like a billboard), the QR code needs to be significantly larger.
3. Quiet Zone
Leave enough "quiet zone" (white space) around the code. This helps the scanner identify where the data starts and ends.