Preface
Until November 2007 my e-mail-handling was a MESS! My inbox was full of JUNK and I had no SYSTEM. So basically I started hating e-mail. But then on my trip to Silicon Valley I finally read David Allen’s Getting Things Done and things started changing. I’m using the system for almost 4 months now and it works TREMENDOUSLY well, meaning that my productivity and responsiveness has increased significantly.
Step 1: Get yourself a Gmail account

Gmail is my primary email-software. I’ve centralized all emails in gmail and I have one private and one professional account. I’m using Gmail primarily for over 2 years now and I’m very happy.
Step 2: Prepare 3 simple labels/folders

That’s all you need. Trust me!
Step 3: Process your STUFF every day!
Go to your inbox, pick one email at a time and decide among the following options:
a) If you can answer within 2 minutes, answer now. If you don’t have 2 minutes, label it @ACTION.
b) If you can’t answer within 2 minutes, choose @ACTION or @SOMEDAY/MAYBE.
c) If it’s junk, archive or delete.
d) If it’s regulary junk, put up a filter.
If you write an email and know you will have to follow-up or need something back, then go to your Sent Mail and label it with @WAITING FOR.
Don’t forget to delegate. If something can be done by someone else more efficiently, then delegate it and label the Sent Mail with @WAITING FOR.
When you’re done processing your inbox, go to your three labels and review everything regularly to have a complete overview. Caution: Don’t forget to actually DO the emails in your @ACTION box!!!
Very important: It’s crucial that you process 100% of your e-mails. Get your inbox to ZERO!!! I do it every day a couple of times and it feels GREAT!
DONE!

YES!!!
PS: As you may see in the last picture, I have also the labels @CONSULTING and @PARTNERSHIPS. These are individual modifications. Feel free to make adjustments according to your requirements. GTD is a very flexible system.
PPS: I recommend reading the GTD-book before starting. It will give you a better understanding of the whole system.
PPPS: I also found a useful video called “Inbox Zero”