Google began experimenting with the concept of mobile-first indexing for its search tool about a year ago, and the company has now released some tips for how webmasters can improve their sites' rankings in the new system. The list of tips includes a lot of common sense things like making sure the content and metadata of the mobile and desktop versions of the site align, along with some more technical advice. The blog post containing the tips also has a link to a special tool that webmasters can point to their website and have it crawled by a Googlebot smartphone. This crawl will reveal whether your site is mobile-friendly, and what you can do to make it better. Resource conflicts, things that didn't load correctly, and other issues that may affect your site's usability and indexing are also shown.
Google has been cracking down on mobile sites that don't have content parity with their desktop counterparts in its AMP rollout, and that same mistake will now cause webmasters to see their sites ranked lower in Google search results for searches done from mobile devices. Structured data and metadata are obviously important, as well. For sites that use a separate host server when pushing the mobile version, there are also some listed best practices regarding hreflang and the rel=canonical and link rel=alternate properties. Naturally, these sites should also make sure that the separate mobile servers have enough capacity to handle an increased number of visits from search crawlers.
Google's push toward catering to the mobile crowd in regards to search, page serving, and other aspects is not quite in full swing yet. This effort, for example, is still on a slow and limited rollout. Google has been a bit more aggressive in regards to rolling out its AMP initiative, serving optimized pages on mobile platforms, so long as webmasters take the initiative to make the content on their pages AMP-compliant. According to Google's data, a majority of traffic on its service comes from mobile devices, which isn't terribly surprising considering the popularity of Android and the fact that Google has paid out to Apple so that its search service remains the default on iOS.