If you want to play 'Tell Me Why' by Neil Young on acoustic guitar you should first tune your guitar down a whole step for every string. First, the chords are in a Key of G. The chords you will play with are G, D, C, Am7, Gmaj7 and a Bm. Also on certain parts of the song you should lift up your index finger on the C. The verse will be C, D, Am7 and G. This is a boom-chucka rhythm which means you play the root note and go down up on the chord. You can throw in licks by lifting up your index finger and hammer on the d string in your C. Next on the D you just alternate the boom-chucka from a D note to an A note. On the G, you can also do a G run and whenever you do runs you should always try and keep your chord shapes. On the tell me why part you should play C, C, C and then a G. Next play D to a C, to an Bm and then to Em. Following these chord progression you can play the song.