If you understand the anatomy of the heart you will see how V5 and V6 give a good measure of the lateral, left side of the heart while V1 and V2 cover more of the septal area.
By understanding where the leads are positioned and knowing the anatomy of the heart, one can better understand where a certain abnormality is occurring in the heart, and which artery is likely involved:
Finally, the Rhythm Strip is important because it gives you the most time in one lead for observing the Rhythm. Recall that the entire ECG is 10 seconds long. The rhythm strip gives you all 10 seconds of the chosen lead (in this case lead I). The other leads are being sampled sequentially: that is the first 2.5 seconds of I, II, III are recorded, followed by the next 2.5 seconds of aVR, aVL, and aVF, etc...
Later I will write about how to place the leads in real life and briefly touch on what “augmented” means, although as long as you know the direction in which the leads measure you will be able to interpret ECGs.