Have a place for everything
This means your keys, your wallet, your office supplies, etc. If everything has its place, it’s pretty hard to lose anything once you learn where that place is. Files are in the file cabinet, my keys hang by the door, and my wallet goes on the little table in the hall. There is no mad scramble to get out the door as I know where everything is!
One thing in, one thing out
When you get new bright cushions, get rid of the old faded cushions. When your kids get a new toy, help them pick out a toy that they’ve outgrown.
Purge twice a year
Make it a point to spend a day or two twice a year doing nothing but purging.
Keep a basket in every room
Despite your best ongoing efforts, stuff from one room inevitably finds its way into another. Keep a small basket in each room of the house. Each evening, put the out-of-place items in the baskets, and each morning, return them to their proper place.
The more storage you have, the more stuff you’ll keep. Instead, have limited storage and if stuff doesn’t fit in there, get rid of it.