These ideas work for just about every type of UN-STUFF-ing you need to do. Some of them will work for you, some of them won't, but there's bound to be at least one tip that can help you reduce your stuff in both time and space.
General tip # 1: Have the right tools, and have them on hand.
If you're doing paperwork, you know you'll need lots of little stationery gizmos. If they're in a drawer near your desk, you'll use them and finish the job. If not, you're likely to think "Oh, I have to get the stapler from the kitchen, and the stamps are out in the shed, and it's all just too much trouble so I'll stop here". Make it easy for yourself.
And get ones that work properly. If your filing cabinet makes an unholy screeching noise when you open a drawer, you won't want to use it. If your stove singes your eyebrows every time you light it, you'll be reluctant to cook without a fire-proof suit.
General tip # 2: Do it when you think of it.
If you're brushing your teeth and you notice the basin needs cleaning, then give it a quick swipe while you're there. Or if you suddenly think "Oh, I must remember to check when the electricity bill is due", then head for your files and drag it out.
And as above, keep the tools on hand. A sponge in the bathroom means you can give that basin a quick swipe, just like some stamps in your top drawer means you can post that letter.
General tip # 3: Avoid creating more mess than you need to.
If you're clearing out a room, don't empty everything into the lounge. Chances are, you'll get halfway through and then feel like it's all too much. Do one cupboard at a time, or one category at a time. If you're going through your paperwork, only go through one file at a time.