When we talk about reading a 12 lead EKG, we have to talk about the term contiguous. Contiguous leads are next to each other, anatomically speaking. They are all touching, and in the same general region (like the left ventricle, for example).
For contiguous leads, I came up with my “Two-Fer” rule. The Two-Fer Rule means you need two leads looking at the same area of the heart to show the same problem. ST segment elevation or ST segment depression.

Looking at the EKG

Now contiguous leads show lateral as I/AVL and V5/V6. Look at the color blue – it’s your circumflex artery. Red is your inferior, II/III AVF or your RCA. Your right coronary artery. Finally, green is your LAD, V3 and V4.
When you look at the 12 lead EKG, it represents itself by this color coding, where I/AVL is your high lateral, V5/V6 is your low lateral. Take a look at that red triangle – this is your inferior leads and if you take a unique look at that, it kind of looks like a high heeled shoe, right?
Use that red shoe so you can think of those foot leads as your inferior. Then green represents your anterior or your wall. V3 and V4. And blue as your circumflex artery.
Check out this YouTube video to learn my mnemonics used to help remember coronary blood flow and contiguous leads on the 12 lead EKG.