I believe the easiest way is:
(1) Make sure you have latest version of iTunes.
(2) Update to 2.2 through iTunes.
(3) Jailbreak with one of the "pwn" programs.
This would, however, involve restoring twice. I've heard you can combine steps 2&3 into one step if you use pwnage tool, thus having to restore only once, but that procedure sounded a bit complicated to me.