There are a growing number of resources dedicated to improving web archivability, including tools, examples, and additional recommendations.
Vangelis Banos' web service Archive Ready provides an automated evaluation of some aspects of web archivability, based on a novel framework he proposed in a 2013 research paper. As is the case with accessibility, there are limitations to what archivability issues can be detected using automated tools.
Google Webmaster Tools
Though built primarily to facilitate search engine optimization, Google Webmaster Tools provides a number utilities that can help improve archivability including: robots.txt configuration, emulating crawler access to your website, structured descriptive metadata testing, managing XML sitemaps, broken link checking, soft 404 detection, identifying crawler traps, and title and description quality testing.
Internet Archive Wayback Machine
Since many web archives use the same technologies, plugging a web address into the Internet Archive Wayback Machine and clicking around can give you a quick sense of whether there are major barriers to the archiving or re-presentation of your content.
UK National Archives guidance
The UK National Archives published "The UK Government Web Archive: Guidance for digital and records management teams" in 2016, a resource which outlines the activities entailed in web archiving, limitations of contemporary web archiving technologies, and recommendations for webmasters. It is written in a very accessible manner and should be considered a more generic resource beyond the intended audience of UK government webmasters.
Portuguese Web Archive guidance
The Portuguese Web Archive's 2010 "Recommendations for authors to enable web archiving" offers categorized and prioritized tips on many dimensions of web archivability.
Columbia University Libraries guidance
As part of their Web Resources Archiving Collaboration grant from the Andrew W. Mellon Foundation, Columbia University Libraries is developing guidelines for archivable websites in particular for outreach to web builders whose content they are archiving.
National Library of Australia guidance
The National Library of Australia produced some early, now archived, web archivability guidance in 2002 titled, "Safeguarding Australia's Web Resources: Guidelines for Creators and Publishers". They also offer a companion 2001 document titled, "Managing Web Resources for Persistent Access" that focuses more specifically on website content organization and link persistence.
Presentations and blog posts
Several presentations (2014, 2012) and a 2012 blog post by Nicholas Taylor recap much of the same guidance presented on this portal. A 2011 blog post by Robin Camille Davis distills the recommendations down to the five most essential.