Slipstick Systems first wrote about this in 2001 and it's still a very useful tip 12 years and four versions later.
One of the biggest problems with email is prioritizing messages. If you deal with messages in the order that they arrived, you will probably find yourself spending too much time on unimportant messages and not enough on the important items.
Perhaps you skim down the list of messages and use your eyes and memory to make a mental list of what order to deal with messages. Alas, this is very hard to do. Not only are eyes and brains error-prone, but the list keeps changing!
If you've tried Outlook's Rules Wizard to group related messages in various folders, you might have had a hard time keeping track of your "to-do" messages (messages to read, respond to, or act on). It's easier to keep track of "to-do" messages when they are all in one folder.
I have good news for you: there is a workable alternative. Instead of using the Rules Wizard to move messages to folders, use rules to assign a category to each message. Then create a view that groups messages by the Category field and voila! Your messages can all stay in your Inbox, but they will be organized in groups. (Outlook won't let you sort your messages by Category, but a nice side effect of groups is that you can expand and collapse groups by clicking on the +/- in the group heading.)
Furthermore, if you put a letter at the beginning of each category, you can easily force them to alphabetize in priority order. For example, you could use the category names a-Spouse, b-Boss, c-Coworkers, all the way down to z-Spam. This way, your Inbox will be prioritized as well as organized.
And, if you move messages out of your Inbox when you are done with them, it will be very easy to keep track of your "to-do" messages. In the next newsletter, I'll discuss efficient ways to move finished messages out of your Inbox.
This tip is adapted from "Overcome Email Overload with Microsoft Outlook 2000 and Outlook 2002" by Kaitlin Duck Sherwood. This book is long out-of-print but a PDF is available on the authors website. The screenshots and menus have changed and some features are no longer available, but many of the email management suggestions can be adapted to current versions of Outlook.