I reckon that my biggest "secret" to inbox zero is no secret at all. It's based heavily on David Allen's Getting Things Done book, and consists primarily of quickly answering a few escalating questions about each email message in my inbox:

1. What does this message mean to me, and why do I care?
2. What action, if any, does this message require of me?
3. What's the most elegant way to close out this message and the nested action it contains?

Not very earth-shattering stuff until you consider how much of the crap in your own inbox may never have been subjected to these simple filters.

Fifty percent or more of your mail may not make it past the first question: delete. A majority of the remainder may not make it past the second (beyond perhaps a one- or two-line reply). And, God willing, you'll eventually get really fast at dispensing the rest with quick application of the third. The key is to get super-fast at turning valuable messages into actions or placeholders for action. I'll say it again:

You're in the business of making sandwiches -- not deciding the prettiest way to stack the customers’ orders.

Notice in particular, that each of these three questions frames your activity around the best use of your interest, time, and attention. You're mentally filtering each message -- turning it like a piece from a jigsaw puzzle -- to see whether it has a fit in your world right now. It only gets a train ticket to Actionville on your say-so. Don't fill that train with hobos and freeloaders.

So, go. Look through your pile right now. How many messages don't even make it past the first question? How many can you delete right this second? Set a timer for ten minutes, and try to process one screenful -- two if you can manage it -- and see how you do. Remember, this is your decision-making and priorities that govern the attention each message gets, not the fact that the request on your time simply exists in the world; that's probably the thinking that got you here, right?

This doesn't make you an impatient jerk. It just means that you've learned what happens when you don't put a value on your own time and attention; you can't afford to say "yes" to every item that's lobbed over your transom.

Focus on finding the fastest and straightest path from discovery to completion, and your inbox fu will be strong.