Perhaps you've been hearing about GTD for a while now. Maybe you've even read some of my posts on this topic. But for some reason you didn't do yourself the favor of picking up the book and changing your organizational habits. I certainly recommend you read Allen's book if you want to understand the full concept of GTD. I've even found reading the book two, three, or four times to be immensely helpful. However, there are things you can do to test the GTD waters without going through the book.
The Omni Group, makers of the popular OmniFocus software, have released a free PDF that serves as a crash course in the bare essentials of GTD and how GTD is applied in OmniFocus. It does have a very direct spin towards the use of OmniFocus on the Mac but it's a great read nonetheless. If you're struggling to find the time to read the entire Getting Things Done book, download the PDF and see if it's the jumpstart you need.