Step-by-step, this is what you should do:
You should create two new folders in your e-mail program, directly below your Inbox; I call them Hot Stuff and Old Stuff
a) The Hot Stuff Folder
You should move messages from your Inbox to your Hot Stuff folder if they require any action on your part, even if that action is simply to reply to the e-mail. There are two exceptions to this rule. Firstly if the reply would take less than a minute to complete, do it straight away. Secondly, don't clog up your Hot Stuff folder with reminder e-mails, if the task itself is already on your Yearly Plan, Weekly Plan or Ticklist. If you follow the advice elsewhere on this website, the really important tasks will already be in your plans, or on your Ticklist. Every time you add a message to your Hot Stuff folder, you should also add a brief item to your Ticklist. You should review your Hot Stuff folder daily, moving completed items to the Old Stuff folder, and reviewing the priority of other tasks. This last task should take less than two minutes.
I also drop messages into the Hot Stuff folder if I know I am likely to need them in the next week.
b) The Old Stuff Folder
The vast majority of e-mails that you receive – especially if you are a relatively junior member of staff – will be stuff that you don't actually need at the moment, but that you might-maybe-possibly need at some time in the future. Make a decision for each item that arrives in your inbox: do you need this now? If the answer is yes, drop it into your Hot Stuff folder, and add it to your Ticklist. If the answer is no, drop it into your Old Stuff folder.
There are two caveats here. Firstly, make sure that the title of the message is clear enough for you to be able to find the message if you need it; and secondly make sure you know how to use the Search facility in your e-mail program. Your Old Stuff folder is going to become a library of material that you can search, containing minutes of meetings, statistics, policies and reports. Anything that you may need to look at in the future ends up in Old Stuff. Many books on personal organisation will recommend many more folders and sub-folders than the two described here, but that is rarely appropriate for a chalkface teacher. You don't want to debate with yourself about which folder to drop a message in: keep it simple.