Key principles of Mobile First Web Development include a focus on simplicity, prioritizing content, utilizing responsive design techniques, optimizing performance, and incorporating touch-friendly interactions. Designers and developers should aim to deliver an intuitive and seamless experience across devices, ensuring that the most critical information is readily available on mobile screens.

While responsive design is important, there is a fundamental difference between Mobile First design and responsive design. Responsive design aims to adapt a website's layout for different devices, while Mobile First Design starts with designing specifically for mobile and then expands to larger screens. Mobile First Design places emphasis on optimizing for smaller screens, ensuring efficient content delivery and functionality.

To create an effective Mobile First website, start by understanding your users and their behaviors. Analyze your site's traffic to identify the most popular devices and tailor your design accordingly. Utilize a mobile-friendly design framework, keep your menus and navigation simple and easy to use, and prioritize important content by making it prominent on mobile screens.