A QR code is only useful if phones can scan it quickly. That means a high-contrast design, enough quiet space around the code, and a destination that still works.
Pick the QR type that matches your content: URL for websites, Wi-Fi for network access, or text for short messages.
Keep the design simple. High contrast between the modules and background helps scanners more than decorative colors.
Test the code on more than one phone before you print it on packaging, posters, or business cards.
When the scan opens the right result every time, download a high-resolution version for print and a lighter version for screens.