To do the intro for Even Rats as easy as possible, heres what you should do.
1)Barre the G B and high E strings at the second fret with your index finger, creating a D7 chord
2)Stretch your middle finger to the third fret on the low E string
3) Put your ring finger on the 3rd fret of the B string, creating a D/G chord
4) To hammer-on the 4th fret* on the G string, use your pinky
Guitar 1 (0:02-0:20)e|-------------2---|-------------2----|-------------2---|--------------2---|B|---2h4*--------3-|---2h4*--------3--|---2h4*--------3-|---2h4*---------3-|G|-----------------|------------------|-----------------|------------------|D|-----------------|------------------|-----------------|------------------|A|-----------------|------------------|-----------------|-3--------3-------|E|-3-------3-------|-3-------3--------|-0-------0-------|------------------|
Guitar 2 (0:10-0:20) *position relevant to above ^*e|-------3--------3--------3---------3--------0--------0---------0--------0-|B|-------3--------3--------3---------3--------0--------0---------1--------1-|G|-------0--------0--------0---------0--------0--------0---------0--------0-|D|-------0--------0--------0---------0--------2--------2---------2--------2-|A|-------2--------2--------2---------2--------2--------2---------3--------3-|E|-------3--------3--------3---------3--------0--------0--------------------|
0:21 (Both Guitars)e|-3-3-3-3-3-3-3---|B|-3-3-3-3-3-3-3---|G|-0-0-0-0-0-0-0---|D|-2-2-2-2-2-2-2---|A|-3-3-3-3-3-3-3---|E|-----------------|