Kid's stuff has a way of taking over homes and leaving parents frustrated and defeated. I remember one client saying, "It's like it's become my kids' home and I no longer have a say." The things that belong to kids often goes unquestioned. But that hurts your peace of mind, which your kids will feel.
So let's grab some trash bags and start with toys. Kids often have more toys than they can play with. Whenever anyone has more than they can use, it tends to spill out. Parents often try and solve this by purchasing storage containers. But I've found the best solution is to go through the toys and see what's no longer essential. What doesn't your child play with anymore? You can also have your child present in this process. The main thing is to keep it super simple and unleading.
I like sitting on the floor, kid level, and asking, "Do you play with this, or could we let it go?" I have no opinion. I'm only interested in their reaction. It might be more difficult since you spent the money on the toy, or you want your kid to love the toy. But you're here to be of service to your child and you want to help her separate out the things that no longer matter to her. Put the toys your kid no longer wants into the charity bags and tie the tops so they won't get curious by the contents.
Next, let's look at your child's art. Parents often get overwhelmed by the massive influx of their kid's art. I remember a client whose entire alcove was a storehouse for her childrens' art. She was fearful to throw anything out. I think she was afraid of hurting her daughters' feelings. But I had her kids come into the room and they all went through the art and tossed most of it. Together they decided to put the art work in two portfolios. If you decide to do this on your own, ask yourself, "Which of these pieces of art are most special to me?" Or, "What would I frame today?"
Lastly, let's go through your child's clothes. This is great to do with your child because you are helping him make decisions in a simple way, by what no longer fits. I did this recently with a kid. I opened a drawer, took out a shirt, held it up, and asked, "Do you wear this or can we let it go?" He kept some, but a lot of it was too small. I felt this gave him confidence.
The thought of doing this work can be daunting. But it helps to know that the presence of things that are no longer a part of your child's life brings chaos and disorder. Getting rid of the clutter will give you needed peace of mind, and this helps you be a better parent. I'm available to help if you feel stuck. I live in Chicago. But I can work anywhere by online video clutter busts via iChat or Skype and I'm great at working directly with kids. I'm at firstname.lastname@example.org