So I was reading the latest in Samuel A. Rebelsky's saga on getting to Inbox zero, and I thought I'd mention how I do it.
I seem to get about 200 work emails / day, and in my personal email, maybe 150. Much of it is unimportant. Some of it is urgent. My Inbox Zero strategy is about marking the important items with a star, doing the urgent items right away, and archiving the rest: A bit like the Eisenhower box (from Wikipedia):
I make a fairly modest use of labels, largely because most of my email is forgettable and I can usually find what I want with search. For almost all of my labels, I bypass the Inbox. I figure that if I have a label for it, I can rely on the visual cue (label name bolding) that there is something unread. I rarely delete email.
I'm doing this with GMail. The key feature I depend on is that I can set a checkbox for all of the email that I'm reviewing. It also helps that in GMail the checkbox selections are sticky, so that I can apply sequentially more than one operation to the same collection.