There isn't one method that works for everyone, but here are some suggestions to get you going. In some cases, you will need to work with your child to get that room looking as good as it can Sometimes a clean slate and a respite from the nagging is good for the family.
Make the Bed(s) First
Whether you or your child does it, always make the beds first. Beds make terrific surfaces for organising toys, games and books. Not only do you lose have the space when the covers are crumpled up in the middle, you risk needing to re-wash sheets. If nothing else, just seeing the bed (or beds) made when you walk back into the room, can help raise morale. You may barely be able to make it over the piles without crushing a Lego or two, but this is always the place to start.
Move the Dirty Dishes
Take any dishes out of the room. You can usually spot these on the bedside table or at your child's desk. Better yet, have your child run these items over to the kitchen for you. In fact, remove anything you can see that doesn't belong in your child's bedroom. Getting these items out early in the game saves you the trip when you are running low on energy. It also reduces any piles you need to move around later.
The Garbage Bag and Laundry Basket
You will probably need a big garbage bag and a whole laundry basket to get through this job, but leave them outside the bedroom door. As you grab your garbage bag, also pick up a number of small plastic shopping bags and leave all but one in the hallway. Take one in with you to tackle the first area of the room. As you go around the room, work off the one small garbage bag and make small piles of dirty laundry. Keep pushing the laundry pile towards the door until it is too big, then toss everything into the laundry basket. Don't worry about sorting it now, you can do that when you are feeling satisfied with your work. And when your small plastic bag is full, drop it into your larger garbage bag. This system helps to clear items from the room.
Getting Your Child Involved
Whether you have your helper with you whole the time or just as you actually need the help, it is important for children to be involved in the cleaning. Although it is easier to do it on your own, you are only teaching your child that you will clean up his mistakes when push comes to shove. Your child must be involved with the tidying process, if not the hard cleaning. Whether they are running dirty dishes to the kitchen, pulling all similar items into a pile or moving small piles of toys to the correct drawer, get them involved.
Skip the Cleaning Supplies... For Now
Leave the vacuum and the dusting spray in the cupboard for now. You may not want to go through the room twice, but you will probably need to. For now the job is getting everything in order. As you go through the room, make a note of areas you need to tackle when the cleaning supplies come in. If your child is "helping" you to clean his room, don't lecture him on the dust or areas that need to be vacuumed - even if you asked him to do those chores last week. The task at hand requires a positive attitude, not demoralization. This will encourage your child to stay as an active participant in the process.
One Big Pile
Every messy room is different. If your child's mess extends from one wall to the next in all directions, with absolutely no rhyme or reason, consider working from the outside in. Push everything towards a central pile. Your child will probably love this part of cleaning, as it really doesn't feel like cleaning. Have her wriggle under the bed and scoop everything out, pushing that towards the center as well. Then slowly chip away at this major pile by making smaller piles of art supplies, board game pieces - anything that justifies a pile. If baby dolls or dress-up clothes don't justify a full pile, don't hesitate to toss them to the opposite edge of the pile. When you have crept to far away to reach your sub-piles without an elbow for support, it is time to put them away. Work around the pile in a circle until you only have those few odds and ends left.
Working Through Quadrants
Instead of one big pile, try working in smaller areas of your child's bedroom. This method tends to work better when there are smaller pockets of clutter, and not an evenly spread mess. Whether you start in the cleanest corner or you want to tackle the challenge first is up to you, just get started. You may find it is easier to do on your own, but the act of dividing and piling will teach your children organization, without them knowing it.
Cleaning is hard work. It is even more difficult for your child. If you have nagged for a clean room for a while, chances are that a bigger mess has accrued since you started asking. Take regular breaks when tackling such a big job. Grab a cup of coffee and let your child zone in front of cartoons for a few moments. Setting a time-limit on breaks may help both of you to get back to work. Just make sure you get back to it.
The Final Touches
Only when everything has been picked up, the garbage taken out and the laundry taken to the laundry room should you pull out the vacuum and duster. Start by dusting and wiping down any sticky surfaces, then move on to vacuuming. Better still, do these tasks on the following night - after your daughter makes her bed once again. Just make sure you don't put it off too long, or it may never get done.
Setting the Scene
Once you have gotten through the hard bits and the room is in perfect order, take the time to talk with your child about cleanliness and what you expect from her in the future. Ask what you can do to motivate her in the future. Set weekly chores and rewards. If a clean bedroom makes everyone more calm, then make sure you help your child to stick to it. The more tools you give your child, the easier it will become for him