This document discusses how to determine a normal sinus rhythm on an ECG. It outlines the four criteria for a normal sinus rhythm: 1) normal P waves, 2) narrow QRS complexes, 3) a QRS following each P wave, and 4) regular grouping of the P wave and QRS complexes. Several example ECG strips are provided and the reader is asked to determine if they show a normal or abnormal rhythm based on these four criteria. The document emphasizes looking for all four criteria when assessing rhythms. It concludes by recommending further reading on different types of abnormal rhythms.