Establish a place for each thing in your house and as you use something put it back where it goes so that it stays organized. Use bins, baskets, container, what-not to put things in.
I agree momoflilangel. I have designated areas for everything. We do not let cleaning up slip for one day, because two days of commotion is awful. I also keep a calendar on my refrigerator to keep all appointments, birthdays, etc straight.