Since Google's
Mobile-first Index [webmasterworld.com] went live (actually even before) I have started designing* pages primarily for mobile phones, then larger mobile devices like tablets & detachable screens, then the classic desktop. One set of pages responsive to all screen sizes, but with a primary focus on mobile.
It is very important to use content in its complete form for all screen sizes and not omit content for smaller screens. I have also been creating slightly shorter content than when I was only designing for Desktop.
My development process is:
• Center - I always start with research & writing content. This content will appear complete on all screen sizes.
• Top - Logo, Contact, Site Search & Navigation (intuitive navigation is especially important for small screens.)
• Right/Left - Sidebar content (optional) for the wider Desktop view. This is lessor value content including product links, affiliate links, ads and events.
• Bottom - Copyright Notice linked to full Copyright page, Site Map link & Privacy Policy link.
I have been experimenting on the location of Social Media sharing links, but have seriously considered not including SM on future pages.
* This approach is for hand-coded markups. If using page creation software like a CMS, some of this may not apply. - - -