Practically speaking, I record the song I want to learn on tape if it's not already.....then I move to the kitchen table with my 20yr old boom box, a guitar, and a little technical device that slows the music down to 1/3 its original speed, if need be. Connect it all up and start working out the chords, first trying to determine what key the song is in. As I work out a chord, I write it down. The finished song is then rewritten with the words and chord changes above the words for a reference.

I'm from the old school, doing all this in analog. Most people use a computer for this.

Neil