Here is a list over all keyboard shortcuts in Mac Os X : http://support.apple.com/kb/HT1343 It's hard to memorize all this, but I put them into a learning by repetition program named Genius.App. Genius can be found here: http://www.macupdate.com/info.php/id/13938

I enter only those shortcuts that I tend to need from whatever App I use. I spend the odd 10 minutes each day repeating keystrokes. The shortcuts seem to stick in the grey matter after a while.