The most common mistakes include tracking vanity metrics that don't connect to business outcomes, including too many KPIs (stick to 5-7), using inconsistent metric definitions across teams, setting unrealistic targets, relying only on lagging indicators without leading indicators, ignoring data latency, omitting context for off-track metrics, and failing to assign ownership and action plans. Fix these by auditing each KPI against a decision test, creating standardized spec cards, balancing leading and lagging indicators, and ensuring every off-track KPI has an owner and due date before distribution.