here are some guides that may help you:

http://lifehacker.com/343328/create-a-keyboard-shortcut-for-any-menu-action-in-any-program

http://installingcats.wordpress.com/2007/11/13/quicksilver-keyboard-shortcuts-fast-browser/

http://tips4mac.blogspot.com/2007/12/creating-keyboard-shortcut.html

http://www.tuaw.com/2008/01/24/mac-101-make-your-own-keyboard-shortcut/

We always suggest that "google is your friend."

hope this helps. =)