The Moz website has created a superb “Tech SEO (+ Beyond) Site Audit Checklist” which is available free, without registration. It’s presented in the form of a Google Sheet with over 70 items that may need checking on your website, with – and here’s the good bit – a link explaining each one.
Each audit point is marked with a level of importance (High, Medium, Low) but you can modify these values based on your individual needs. As you work through the audit, you can mark each item with Pass or Fail. Typically you might apply it on a page by page basis.
The items come under the following headings:
2. Crawling & Indexing
3. Meta & Structured Data
5. Links & Navigation
11. International & Multilingual Sites