This is an excellent book. If you find yourself overwhelmed with too much to do and not enough time, or just find yourself disorganized frequently, his system is a great start. You should really just go buy this one.
First he recommends you go out and get yourself a label maker, a bunch of folders, and get them ready.
The process will take place in five big steps. Take this seriously for a second...
(1) collect (2) process (3) organize (4) decide (5) act REVIEW weekly.
(1) collect Clear your head of any thoughts you have to do related to work, life, love, spirituality, friendships, bills, and collect of of these thoughts on separate pieces of paper. use recycled paper.
(2) process Then process this giant pile... your inbox... into folders. Follow Allen's two-minute rule. If there's anything you can do right now in two minutes or less, then do it now, thus freeing up your time and mind. See also: Quadrant 1 (Covey). The reason some of us can't sleep well he says, is because there are a lot of leftover "to-do" floating around in our head. Everytime you have a thought, make a commitment, or get a new responsibility - write it down.
(3) organize Is it simple or complex? Simple Issues: schedule time to solve problem (will it take 1 hr or 3-4 hours?) Complex Issues: break into simple issues, schedule like above into a calendar. He uses a Palm Pilot / Pocket PC like device (maybe even a tablet PC at times). Create a "waiting for" list for things that require other people's time.
Schedule your tasks and create folders for everything (label makers make it fun).
(4) decide Can you finish it in two minutes? if yes, finish it. If not, keep it see above.
(5) act Follow your schedule and live your life... don't worry if you screw up, review weekly and you will get better.
He also recommends creating a folder for things you want to do someday/maybe. I added sailing to my someday/maybe and ended up taking a class on sailing this past summer.