Do everything without whining, complaining or arguing. Every one has their own jar. Start off the week with a set amount of quarters in each jar. If they are caught whining or complaining, they lose a quarter. At the end of the week, they get the money that remains. Better than allowance!!!
Use zippered pencil pouches to organize puzzles instead of storing the bulky boxes. Cut off the image from the front of the box and store it in the bag, too. (This blog post has several great ideas for organizing kids toys.)