The easiest way to create clutter in your home is to say "I might use this one day". To find out whether you're creating clutter or being thrifty, weblog Unclutterer recommends treating it like the mate of a sock you recently lost: keep it for a predetermined amount of time, then toss it.
Unclutterer details how it (and many of us) deal with lost socks:
Rarely is [a] missing sock lost forever, so we keep a small basket in the laundry room for single socks and when the mate shows up we immediately know where to find its match.
Even though mates are usually found, invariably one sock will hang out in the lost-mate basket for many months, its mate gone forever. (After seeing Gnomeo and Juliet, I've been blaming lawn gnomes for this phenomenon.) If a sock hangs out in the lost-sock basket for more than three months, the sock is moved to the rag pile and recycled for dusting.
This isn't new to many of you -- though I highly recommend it for those prone to losing socks -- but the trick is to extend this to other areas of your house. Afraid to give that shirt to charity in case you might wear it again? If after three months, you haven't, you can give it to charity. Cupboard overflowing with recycled plastic bags? Toss them after a few months of reuse. It may seem simple, but it's a heck of a lot more effective than just asking yourself if you're "really going to use it again". Hit the link to read more.