I thought it might be interesting to share some tips+tricks we've learned on how to organize our email folders.
I use TheBat and one of the first things i do when i create a new email account is create a bunch of additional inbox folders.
Then i create a filter so that any incoming email from someone i know (in my address book) gets sent to the "Inbox - Known" folder. This helps me identify most of the email that is good.
All other email is filed in "Inbox - To Be Filed"
Then i make a folder called "Inbox - To Reply" where i can move email that needs a reply from me at some point but which i don't answer right away.
I also create 2 top level folders, one for Spam and one for Mailing Lists. I have filters that send any email from a mailing list directly into the Mailing List folder where I ignore it most of the time (my filters also mark it as read so it doesn't distract me). The Mailing List folder has a subfolder called "Read" where I move mail every once and a while after I've glanced at it. Because mailing lists never appear in my normal email inbox to distract me i don't worry about signing up to mailing lists much.
The Incoming Spam mailbox is where spam lives. I actually have subfolders for "Confirmed Spam" which is where i myself personally put spam. The top level is where my filters put it. The reason i do this instead of just deleting spam email is to give myself several chances to go back and look for stuff that might have been mistakenly marked as spam, and to give myself time to see patterns in spam that i might want to add to a filter to help me flag spam.
Picture below [note screenshot captor makes it easy to blur stuff with the blur button

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What tricks do you use?