The single biggest CTA failure mode is too many. A page with 8 different CTAs typically converts worse than the same page with 1 clearly dominant CTA, because every additional choice introduces friction. The classic rule: one primary CTA, one secondary CTA at most, on any given screen.
Specific verbs outperform generic ones. 'Start your free trial' converts better than 'Get started'. 'See the demo' converts better than 'Learn more'. Tested CTA copy is often the single biggest A/B-test win on a landing page.
Placement matters as much as wording. Above-the-fold for high-intent visitors, repeated throughout long pages for context, and a final CTA at the end of long content for readers who reach the bottom. Single-CTA pages without scroll-anchored repetition often under-perform — users who scroll past the hero have no path back.