While some methods recommend only one inbox, you are probably going to have at least a paper and an electronic. You may have several. This is really not a problem as long as they "Cascade" - that is, that they pour into each other so you have one point of contact.

Paper Inboxes
I actually think it's fine to have a lot of paper inboxes, as long as they are all listed on your recipes so that you don't forget one. When you plan, you should actually pour all your paper inboxes into the "Master Inbox" in your office before you start processing.
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Electronic Inboxes
It's difficult to centralize your electronic inboxes before processing, so make sure your recipes list all of your various sources of information and process them in that order.

How to Process your Inbox

How to process your inbox
  1. Maintain Zero Inbox, meaning that before you start actually doing work, process your entire inbox. Don't get sidetracked or led down a rabbit hole. Don't put anything back into the inbox or create new inboxes by making piles on your desk or leaving e-mails read but in your inbox.
  2. Look at each item as it comes in and Deal with it Now. Is it a project, an actionable item, or reference material?
    1. Project - Log into Master Planner for further breakdown during planning time.
    2. Actionable item - Are you doing to do it or are you going to delegate it? If you are going to do it, will it take less than about eight minutes? If so, do it. If not, defer it either onto your Master Planner or into the toaster so it comes back at the right time. If you are delegating it, mark it as such in your Master Planner or toaster.
    3. Reference Material - File it in your Deep Freeze.

Needful Things

Paper Inboxes
Inboxes for paper need to be sturdy, clearly-labeled things. Sturdy so they can survive wear and tear, especially if you are carrying it with you, and clearly-labeled so some well-intentioned church lady (or church lord) does not "helpfully organize" it.

Electronic Inboxes
You don't get to choose much of the software that your information comes in on. Facebook and twitter comes in on a web interface, although you can use third-party tools like tweetdeck. I highly suggest gmail for e-mail, even if it means you have to forward from another address. Why? Really good Spam filtering, great search, access from anywhere and several excellent toaster add-ons, like  Boomerang and Sanebox.  An article with excellent productivity tips for gmail can be found here .

My Implementation

I have the following paper inboxes:
  1. My "master" inbox - a wire basket in the office
  2. My sunday inbox - a wire basket in the sacristry next to the church where I put things parishioners push at me on Sunday mornings and I don't have time to deal with then.
  3. A travelling inbox - a set of folders inside a plastic protector. It has three folders, "Work," "Home," and "Expenses." Any paper that needs to travel goes in there and is in my computer backpack.
  4. My toaster .
When I do my weekly inbox process recipe, I dump all the inboxes into the master and process from the top down, using the described process. Delegation goes to people's mailboxes, reference is (usually) scanned into Evernote , and tasks that take longer than eight minutes are logged into my Master Planner.
My electronic inboxes include:
  1. Voice mail on our church phone system
  2. E-mail, of which I have many addresses, all of which forward to my gmail .
  3. Facebook
  4. My Evernote inbox (which is all reference material that just needs to be sorted, as Evernote is my primary Deep Freeze.)
  5. My Master Planner inbox, which is where I take down tasks I think of on the fly on my iPhone.
When I do my daily communications recipe, I go through them in order following the process described, doing things that take less than eight minutes, using gmail and sanebox to delegate or toast, and sending things to Evernote for reference. Any project or action that will take longer gets logged into my Nozbe Master Planner inbox, which is then processed during my planning time.
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This order is wirtten down in my recipes , and I try to follow it exactly. As always, Forgiveness is Divine .