Ideally, you should have only one or two in boxes, where you go to process “stuff”. Probably one at your desk at home, and possibly one in your office or briefcase/bag. Usually though, this isn’t the case. Most people find themselves with big piles of paper, objects, or other items, in places they really shouldn’t be. Having these piles of unprocessed items really undermines the entire GTD process. Having multiple in boxes not only takes up unnecessary space, but it prevents you from dealing with everything effectively, and you can’t clear your mind (which is the objective, no?).
Go through these piles, and process it in a GTD-like manner. Likely, most need immediate attention, and will probably be items you will need in the future. Try to move any junk into its appropriate place. Anything that requires more thinking or consideration, move to your primary in box.
At the end of the process, you will probably be stuck with some things that you just don't know what to do with. When you get items like this, use the following 3 steps to get rid of them: