I learned on the ECG's for dummies in paramedic school. But like the other post said, it is important to write down the rules and systematically eliminate them. I have taught this subject multiple times and I too still follow the same questions every single time. Is there a p-wave? Is the rhythm regular or irregular? Is the rhythm fast or slow? Is the p-r interval WNL? Is the QRS complex wide or narrow? Is there a p-wave for every QRS complex? Then write down the definition to each of the rhythms you are trying to learn. Ask the same questions every time. I hope this helps.