As I stated earlier, the 1st chord of the song is E minor. The second chord, or IV chord in Am, here we'll use Amadd9. This is a fun voicing that you can use pretty much anywhere you would use an A minor chord if it's stylistically appropriate. I like it because the ninth of the A minor chord is a B note, which we're playing using the open string. This gives us a great jangly open ringing sound that we hear quite a bit in classic rock. On the B minor chord, I'm using a smaller version and voicing of a Bm7 that has no 5th and gives us a nice open sound. We have seen this voicing before on "Painful Memory," but there it's functioned as a dom7#9.
When we switch to the reggae style section it's all about the upbeat—the notes are sounded on it in beat 1, 2, 3 and 4. Very often we use the upstroke for these, but in this particular location I like the sound of the down stroke; frankly the choice is yours on that. As you'll notice, I only use the reggae feel on the E minor chord.