Where x you have to mute string with your hand, but u don't have to pull strings
  
/ - Up
\ - Down

Remember that - Tab is only HELP for you. Tab CAN'T Play!

                      
                           Here u change G on Em (through empty strings)
     G ---u hold G----     |   Em
E-|-----3---x---3-----3---x-0---0---x---0---0--0-0x-------|
B-|-----3---x---0-----0---x-0---0---x---0---0--0-0x-------|
H-|-o---0---x---0-----0---x-0---0---x---0---0--0-0------o-|
G-|-o---0---x---0-----0---x-0---2---x---0---0--0-0x-----o-|
A-|-----2---x-------------x-----2---x---------------------|
E-|-----3---x-------------x-----0---x---------------------|

U can also try playing your own version, chords for intro:

   G(blues)    G(classic)     Em
|--2--|     |--2--|        |--0--|
|--2--|     |--0--|        |--0--|
|--0--|     |--0--|        |--0--|
|--0--|     |--0--|        |--2--|
|--2--|     |--2--|        |--2--|
|--3--|     |--3--|        |--0--|


Other tabs of this song (on this site) have bad intro, But u can find there REST OF THIS SONG.
Have Fun!