So, you want to be a Gmail ninja?
If you got 100 new messages, how long would it take you to get through them all? An hour? Five minutes? How would you find the important ones, reply to the ones that require an immediate reply, and mark the ones that you needed to take care of later? Would you use stars, filters, keyboard shortcuts, labels? What about Gmail Labs like tasks or canned responses?
http://gmailblog.blogspot.com/2009/06/so-you-want-to-be-gmail-ninja.html