Anyone really looking to get stuck into SEO should consider reading The Technical SEO Audit Workbook by Search Engine Journal, a free downloadable guide available in exchange for your contact details. Within the workbook, a technical SEO checklist helps track auditing 60 elements of a site, including robots.txt, XML sitemaps, crawl optimisation, page experience, accessibility, and penalty risk. An on-page SEO checklist walks through auditing 24 elements including tags and content structure, duplicate content, internal links, and structured data. It really is an excellent effort.
In a similar vein, I’d also still recommend Hobo SEO’s Free SEO checklist which I’ve mentioned here before. This is a collection of online spreadsheets to help manage an SEO project from both a site-wide level and a page-level perspective.