my guitar teacher gave this to me, so give him the credit ;)

b=bend

riff A   (A7)
e-----------------------------------
B-----------------------------------
G----2--0--2-----0--2--0------------
D----2--0--2-----0--2--0------------
A-0------------------------3b-------
E-----------------------------------

riff B    (D7)
e----------------2------------
B-------1--1------------------
G----2--------2---------------
D-0---------------------------
A-----------------------------
E-----------------------------

riff C    (E7 and D7)
e------------------------------2----------2-
B--------5----------5----------1----------1-
G--------7----------7----------2----------2-
D--------6----------6-----0--0------0--0----
A--------7----------7-----------------------
E-0--0-------0--0---------------------------

riff D    (E7)
e-----------------------------------
B-----------------------------------
G----------1------------------------
D-------0---------------------------
A----2------------------------------
E-0---------------------------------

riff A x4
riff B x2
riff A x2
riff C x1
riff A x1
riff D x1
just keep repeating that