Common pitfalls include leaving pumps running under freezing ice, failing to remove leaves and debris before winter, improperly staging aquatic plants in too shallow water, continuing algaecide treatments during dormancy, and feeding fish excessively as temperatures fall. Also, neglecting to maintain an ice-free vent hole reduces oxygen and harms fish. Avoid these by following a thorough six-step winterization checklist focusing on debris control, equipment storage, plant staging, feeding adjustments, chemical pauses, and ice management.