I simply have two folders: my inbox, and a subfolder called "archive". My inbox is my todo-list. If any message needs further attention, or has some action that needs to be completed, or I'm waiting for an answer for something, it stays in the inbox. If it's handled, I move it to the archive.
Therefore, if it's in the inbox, it reminds me of the stuff that I still need to do everytime I check my e-mail.
Search indexing in Outlook with Vista makes searching through e-mails just as much fun as it is with Google Mail, so you can apply the same strategy as they did. Why delete an e-mail?
Also, I turn off auto-archiving and keep all e-mails local with me.
