Compare the two addresses
Check the final address after redirects and the canonical in the page source. A clean path, a .html path or a campaign parameter can refer to similar content. Establish which page should be the preferred destination.
Make sure the destination is useful
Open the preferred page and confirm it loads, contains the intended content and is suitable for search. A service page should not point to an unrelated homepage simply to remove a warning.
Bring the signals together
Where appropriate, align canonical tags, internal links, redirects and sitemap entries. Google treats these as signals and may select a different canonical. The owner can inspect its selected version in Search Console.
Plan the change before publishing
List the affected pages, preserve necessary redirects and test important links. A small warning does not justify a rushed site-wide URL migration. Recheck the chosen page after the change.
Further reading: Google: canonical URL guidance (opens in a new tab).