To check mobile responsive design, begin by adjusting your browser window's size to observe how content reflows. Utilize online tools like Google’s Mobile-Friendly Test to assess usability on various devices. Pay attention to key factors such as font size, button placement, and image scaling. Testing on multiple smartphones and tablets provides practical insights into user experience. Ensure navigation is intuitive, allowing easy access to all site features. Regularly review and update your design to adapt to new devices and screen sizes. A well-optimized mobile experience not only enhances user satisfaction but also boosts your site's SEO performance.