1. What is the pulse? How many beats?
2. What note is home?
3. Find that note on the low E string of the guitar, starting on the open E and playing every note from there to the 12th fret if necessary.
4. Is it major or minor? Play a major and minor bar chord shape over that note.
5. Map out the key
I, IV, V chords and relative minor iv, ii, and iii chords.
i, iv, v chords and relative major III, VI, VII chords.
Here’s an example of a song breakdown I did on a Facebook live video for Fretboard101 (I didn’t realize it would record in mirrow mode, so unfortunately it is backwards at the moment):