Making a website mobile-friendly involves several key steps. First, consider using a responsive design, which automatically adjusts the layout based on the device's screen size. This ensures that the website looks and functions well on any device, from desktops to smartphones. Second, optimize your images and other media to load quickly on mobile devices. Slow load times can deter users and negatively impact your site's SEO. Lastly, simplify your navigation and make buttons large enough for easy tapping. These changes can significantly improve the user experience on mobile devices.