The noindex meta tag (`<meta name="robots" content="noindex">`) is the proper way to prevent specific pages from appearing in search results while still allowing them to be crawled and to pass link equity. Appropriate uses: (1) Form-submission thank-you pages — they exist to confirm a conversion, not to be discovered via search; (2) Internal site-search result pages — they create infinite low-value URL variants; (3) Filter/parameter combinations on e-commerce that do not represent commercially viable landing pages; (4) Low-value paginated archives (e.g., page 47 of a blog category); (5) Admin or staging pages that accidentally became publicly accessible; (6) Duplicate or near-duplicate content variants where rel=canonical is not appropriate; (7) Tag pages on WordPress sites that fragment topical authority. Common mistakes: (1) Noindexing important pages by accident (most common via plugin misconfigurations or template-level changes); (2) Combining noindex with disallow in robots.txt — Google cannot see the noindex tag if blocked from crawling; (3) Noindexing sitewide instead of per-page during staging; (4) Forgetting to remove noindex when migrating content from staging to production. Audit noindex coverage quarterly.