Inside the guide
Separate the stages
Discovery, fetching, indexing and ranking are different problems. First establish which stage is failing using available first-party evidence. A page that was crawled but not selected for indexing needs a different investigation from one a crawler never found.
Reduce avoidable URL work
Review parameter spaces, duplicates, redirect chains, errors and slow responses. Link to final canonical URLs and use accurate sitemaps. Prioritize changes from the size and behavior of the real site, not an arbitrary crawl target.
Work through the guide
Use the downloadable guide for its complete examples, audit checks and reference list. Record the page or entity reviewed, the evidence available, unresolved questions, an action owner and a review date. Keep assumptions separate from observed findings.