Play some 2-5-1 chords in major & minor – Am D7 G & Am D7 Gm, respectively. Get your ear used to that and then work on more difficult voicings, e.g. Am7 D9 GMaj7 & Am7b5 D7b9 Gm9. As you play through the chords, look at one string at a time and see what note changes are being made. Some notes...