If you're spring cleaning and de-cluttering, it's important to have systems in place so that the clutter doesn't return. (at least not too quickly!) People have lots of little rules they follow to ward off clutter, but we have one simple philosophy...Whenever we buy something new, we MUST get rid of something. This works for us because it makes us think twice about new purchases. If something's not worn out enough to be tossed, we don't need to buy a new one.
This applies to children's toys as well. If our daughter receives something new, we try to donate something else she is done with. Following this rule keeps us from dealing with a huge pile of clutter at any one time.