The golden rule of A/B testing is to look beyond validation and prioritize projects that have the potential for meaningful insights, rather than just validating bad ideas. This requires adhering to best practices and asking the right questions before running a test, including considering statistical power and sample size to differentiate between actual effects and noise. By focusing on projects with bigger potential upside, companies can ensure they're allocating resources effectively and not wasting time on tests that won't yield significant results.