The rest of our clutter comes from the normal places. We have kids so there are outgrown clothes, outgrown gear, art, toys, books, and other detrius kids produce. My husband and I both see how well-intentioned home projects, craft projects, and mail all contribute to the piles stashed around the house. It's time to sort and move on.
1) Let Go
Make a mental shift. It feels like a loss to get rid of something that's actually useful or valuable. Consider the stress you're incurring by having to search for the things you need that get lost in the clutter. Is there anything more maddening than not being able to find the remote, the keys, or the kids when you need them? When I was taking photos of my kids, but framing the shot to avoid clutter in the background, I knew I needed to do more.
Exhibit A- cluttered background
Exhibit B- slightly less cluttered background. Clever, yes?
Clutter can keep you from enjoying what's available to you now. If you haven't used something in the last year, time to move it on to someone who can benefit from it today. If some of your extra stuff is actually useful it'll be even easier to figure out where it should go in step 2.
Sort out everything that's keeping you from clear useable space. If you like, try selling your stuff, but have a backup plan that will move the item out of your house if it doesn't sell in a reasonable amount of time. Here are some resources to help you here:
Sell- Ebay, Craigslist, community garage sales
Give- local children's charities, salvationarmy.org for large things like mattresses and furniture, local Yahool freecycle group, Craigslist, Dress For Success
This is potentially the hardest, as old habits sneak back in. Realize that decluttering is an ongoing process and devote just a bit of time each day to clearing & storing. Make it part of a routine, perhaps something you do before dessert or during commercials. Set a timer. Make your family a chore chart. Find a way to gently remind yourself of the slip and get back on track. Eventually, you'll be enjoying your clutter-free space so much that it will take less time to maintain than to clean again. Good luck!