For those of you who are unfamiliar with responsive design, it’s the idea that you can deliver the same HTML code regardless of screen size, but use CSS to rearrange those elements based on the screen width.
For sites that are not complex, I start with a Mobile-First design, whereby I design the mobile site first, and then expand into pages for tablets and desktops. There’s nothing you can put on a mobile page that can’t be loaded on the desktop version.
For more complex pages, I start by figuring out which elements of a desktop page need to be on a mobile page, and then work my way up from those considerations.