The most common mistake is treating GEO as a separate initiative from SEO instead of a layer on top of it — chasing llms.txt and schema while ignoring weak organic rankings, which are still the foundation AI answers draw from. Close behind: blocking AI crawlers by accident in robots.txt, burying direct answers under marketing copy instead of leading with them, and JavaScript-only rendering that leaves crawlers with nothing to read.
The quieter mistake is inconsistency — publishing a stat or claim on one page that contradicts another page or a third-party mention, which undermines the cross-checking AI assistants increasingly do before citing a source.