• Start from the user's top three tasks; design those screens first
• Follow the platform guidelines: Apple Human Interface Guidelines and Google Material Design
• Touch targets at least 44×44 points; readable type; support dark mode and larger text sizes
• Design for offline and slow networks — show progress and cached data
• Ask for permissions (microphone, notifications, location) only when the feature needs them, with a clear reason
• Prototype in Figma before coding

Web skills transfer directly — see HTML & CSS, CSS in Depth and Bootstrap.