Part 1:
http://www.xt660.com/showthread.php?t=20735
Part 2:
http://www.xt660.com/showthread.php?t=20736
Part 3:
http://www.xt660.com/showthread.php?t=20737
Part 4:
http://www.xt660.com/showthread.php?t=20738
Service your steering head bearings:
http://www.xt660.com/showthread.php?t=12483
All the tools needed (or ways to get round needing them) are covered at various points within the threads, just read them though before you start.