Mostly kids just need help learning how to be organized. If you teach yourself good tricks/tips for organization... teach them those tricks and help them put them into practice. Providing them with materials to help them stay organized is a HUGE step in keeping clean. Also, setting a date/time SCHEDULE to have things done by will help. For example, have:
ORGANIZERS/CONTAINERS FOR:
Shoes, toys, books, crafts, etc.
Color-coded, or labeled clothes hampers for colored or white clothes (or however you prefer to sort laundry).
Accessible clothes bars in the closet(so they can hang things up themselves.)
Organized drawers in their dressers (undies/socks, shirts, pants).
CALENDAR:
3:00-4:00pm = homework/snack/play time
4:00-4:45pm = play/free time
4:45-5:00pm = all toys put away before dinner
6:00pm = help with after dinner cleanup
6:30pm+ = family time
RULES = If you keep rules that have to be kept consistently that have consequences for breaking, it will help them stay on track and learn self-discipline. Such as:
-All clothes either hung-up/put in dresser, or sorted into laundry baskets (not on floor=or no dessert, no friends over, no play-station/t.v., etc.).
-Shoes kept in bins (not all over room/house=or extra cleaning duty assigned).
-Books kept on shelf (not all over bed/desk=or have to go to bed 15-20 minutes early, etc.).
Make sure their responsibilities are age appropriate. Make sure they help each other out (if one gets done before the others, they can help the others finish up and then they'll all have more free-time). If the youngsters wish to help out with the big tasks, let them if it's safe. It may take more time, but if they learn in a spirit of wanting to help, they will resent the activity less when they grow up.
Good luck! :-)
One last point... most kids have a one-track-mind... having a checklist (especially for the younger kids) of HOW to clean their room will help them remember which activity they need to do next... ie: pick up toys, pick up shoes, hang up coat, make bed, take dishes to the kitchen, etc.