Crawl Rate Limited by Server Performance
Crawl rate is somewhere between the minimum list of pages Google wants to update, and the maximum number of pages they think it’s safe to crawl without impacting performance. Any new pages discovered can be crawled provided there is some remaining budget, but might get queued up for the next day.
For Long Term Temporary URL Migrations, Use 301
For temporary URL migrations over a long period such as 6 months, a 301 redirect is better than 302 to speed up the move each way.
Don't Use Noindex on Canonicalised Pages
Don’t mix a noindex with a canonical tag to a different page.
High Volumes of Sitewide Links Confuse Google
John recommends against high volumes of sitewide navigation links which make it harder for for Google to understand the connections between the pages.
Google Accepts Canonical Unless They Seem Wrong
Google will try to follow canonical directives by default, but they ignore canonical tags if there are significant content differences, or if a lot of URLs canonicalising to the same page, if they think it’s a mistake.
Disallow Overrides Parameter Removal
URL Parameter settings in Search Console are a hint for Google, and they will validate them periodically. The Robots.txt disallow overrides the parameter removal, so it’s better to use the parameter tool to consolidate duplicate pages instead of disallow.
Content Loaded Via Onclick Won't Be Indexed
Mobile Sites Don't Need to be Indexed
Separate mobile sites should be canonicalising to the desktop page, so you don’t need to submit them to Google via a Sitemap, but it’s still worth adding to Search Console.
Google Follows Secondary Links If the First Is Nofollowed
If you have 2 links on a page to the same target, but one is nofollowed, then Google will just crawl the followable link.
Affiliate Links are OK
Google doesn’t dislike affiliate monetised sites, provided they are good quality sites with some original content.
Disallowed Scripts Don't Generally Cause Penalties
Disallowed scripts which are flagged as errors are only an issue if they affect the displaying of content you want indexed, otherwise it’s OK to leave them disallowed.