This tip is inspired by an inquiry by "Debra" about how to find archived email. Though I cover Archiving in Gmail Tip #12: "Archiving" Explained, I feel that some general email management tips are in order. Managing email within Gmail can be easy or difficult depending on how you handle them. Read on for some simple tips to better manage your email...
First off, when you "archive" an "unlabeled" email message, it simply "drops out" of the Inbox view and is later ONLY accessible from the "All Mail" view. While this is straight forward, it can be cumbersome if you have more than a handful of email messages. The problem with the "All Mail" view is that it includes just that: all email, labeled or otherwise, and Gmail provides no easy way to find "unlabeled" email. To me, an "unlabeled" email is an uncategorized email that has "fallen through the cracks" and must be Labeled. If I don't, short of searching later, I'll never find it again. Why? I currently have over 1600 email message in Gmail, and effective use of Labels and Searching are the only way to manage them effectively.
My general practice is to assign a Label to EVERY email I receive in my Inbox that I'm not going to trash. This way, EVERY email is available through its corresponding Label view.
If you want to "clean up" your unlabeled messages, see my Gmail Tip #22: Advanced Search - Multi-Labeled and Un-Labeled Messages for details on hoe to find "unlabeled" messages.