Broadly speaking, people fall into three groups when it comes to organizing large amounts of information. Searchers opt for minimal work up front on the grounds that they can use tools to find what they’re looking for later. Filers believe that everything has a place and that it should be in that place so they can find it instantly. Taggers are somewhere in between; they depend on search, but like to sprinkle hints around to make it easier for the search engine. You need to know which group you’re in to know which tools will be best for you. Searchers won’t be happy with systems that expect them to do lots of filing, and taggers aren’t impressed with just leaving everything in a heap. The good news is that there is software to support all of these usage patterns by now.

There’s no single structure of folders or mailboxes that works for everyone. If you’re hard-core anti-filing, you can get by with just leaving everything in your inbox forever; I’ve known some very successful e-mail users who have done just that. At the other extreme, you can build up a baroque structure of hundreds of filing folders, which can be great if you actually use it. If you’re going to build up a folder structure, take the time to think about what’s the most important dimension of e-mail recall for you. One failing of most current e-mail applications is that any given message can only be filed in a single folder (well, you can make copies, but who wants to go to all that bother?). So think about what you’re most likely to remember when you want to hunt up a message in the future. If it’s the sender, you should build your hierarchy based on people. If it’s the project, then a set of project folders makes sense. Avoid starting to build a system where you have some folders for people and some for projects; when you get that first e-mail from your boss about the Shoofly project, you’ll be frozen in indecision as your eyes dart back and forth between the Boss folder and the Shoofly folder.

If you’re on the Mac, you’ve got Spotlight, but PC users aren’t so lucky. Searchers on the PC will benefit from installing one of the many applications that will index their e-mail for faster finding in the future: Copernic Desktop Search, Google Desktop, Windows Desktop Search, and X1 are the leading contenders in this category. You’ll want to try more than one to see which one appeals to you most, as they differ in the flexibility of search, their ability to show incremental results, and the usefulness of their previews.

If you’re a filer, don’t neglect that huge folder full of sent items. It might make more sense to create individual Sent Items folders for each client or project, and file the appropriate messages where they’re easy to find. You can even set up rules to do the filing for you.

If you use del.icio.us or Flickr, you understand the power of tags. You can apply that same power to your e-mail with add-ins like Mail Tags (for Mac Mail) or Taglocity (for Outlook). Once you start tagging your mail, you gain the power to search and group by tags, giving you the power of filing in multiple folders without the bother of actually creating the folders.

Mail calls them Smart Mailboxes. Outlook calls them Search Folders. In either case, the idea is the same: you can set up a folder whose contents depend on criteria you set, rather than messages you file in it. Obvious uses include folders for unread mail, old but unanswered mail, mail from particularly important people, and newsletters identified by subject line. Virtual folders are another good way to create the illusion that things are filed in more than one place.

You’ve got a rules engine in your e-mail client; use it. If you file every single message from Joe in the Friends folder, set up a rule to do this for you and save pointless seconds of dragging and dropping. Combine this with a virtual folder showing unread mail and you can have the rule clean out your inbox as soon as the mail arrives.

If you have lots of folders, dragging and dropping messages to file them can get to be, well, a drag. It’s worth your while to find and use an application that streamlines this process. Examples include SpeedFiler for Outlook and Mail Act-On or MsgFiler for Mail on the Mac.