Step One: Unsubscribe to Catalogs, Email Newsletters, Etc.Now unless you actually read said catalogs or newsletters, having these clutter your inbox is just pointless. It creates stress by creating extra junk to wade through and it also tempts you to buy things that you may not have been intending to buy. Get rid of all unnecessary mailers like this by clicking on the "Unsubscribe" button at the bottom of the email (which they are required by law to have).
Step Two: Banish Spam to the Spam FolderOne type of email that you actually don't want to try to "Unsubscribe" to is Spam email. Spam is nothing that you've signed up for and usually takes the form of a chain letter promising good/bad luck or an advertisement for a product that you've never heard of. Responding to these, even to Unsubscribe can actually backfire on you because it let's their spam-bots know you're alive, and you'll end up triggering even MORE spam.
Instead, what you want to do is leave them unopened and unread and send them to your Spam folder. The more you do this, the better your email's Spam filter will be about filtering them out before they ever hit your Inbox.
Step Three: Answer Emails ImmediatelySo now that you've got your Inbox free of any incoming catalogs or spam, the only messages you should be receiving in your Inbox are going to be either personal or business emails, both of which you should respond to in a timely manner anyway (no more than a day, preferably). You don't need to pounce on them within the first five seconds of them being in your inbox, but don't let them sit there for five weeks either. I usually try to check my email 2-3 times a day, just to make sure I catch any client inquiries, respond to emails from friends, etc.
Since I have an iPhone, I actually get new email notifications anywhere I am, so if I see one that I really don't have the time/energy to respond to when I'm on the road, I will keep it as "Unread" until I get home and can deal with it then. Otherwise I open and respond to everything, every time I go into my email. Never leave anything un-dealt-with.
Step Four: Use the Archive FeatureNow I don't know how other email systems work, but Gmail has this awesome feature called Archive. Generally about once a week, I will select EVERYTHING in my InBox and "Archive" it. This is like virtually cleaning off your desk and putting everything into a big filing cabinet. You wouldn't let every piece of paper you've ever touched pile up on your real desk would you? Why do it at your virtual desk then?
Since Gmail is powered by Google, they have a very good Search feature that does very well at retrieving those Archived emails when you need them. You can search a person's name, email address, or even just a phrase that you remember talking about in the email. It's like having your own personal file clerk! Your Inbox will be clean and you'll still be able to quickly find what you're looking for in no time flat!
Have you ever tried to keep your inbox at zero? Would these steps work for you?