I know how difficult it is to get the kids on board with the idea of picking up after themselves and keeping the house looking neat and clean. I don't have one of those "show" houses where the kids are not allowed in certain rooms. My house is lived in and that's the way I like it. I have kids and they need to be able to live in their house.
But I draw the line when they drop whatever it is they're holding and leave it where it lands. Or when they take out something and don't put it away after they finish with it. My husband and I are also guilty of this at times. It's all about laziness.
If everything has its place, put it back in its place when you finish using it. If everyone did this, the house would have much less clutter and maintaining organization would be much easier.
My mom has my kids and my nephews trained very well. She started when they were toddlers and has been consistent. They are not able to take out a new toy until the first toy they played with is put away. And they do it--every time! The trick with kids is, as soon as they start walking around, make a game of cleaning up the toys. As they grow, it will become part of the normal routine. I know my problem is that I've always picked up after them, so they now just assume mom will clean up, pick up, or throw away whatever they used, ate, or played with. Now that they're growing up, it's much more difficult for them to grasp the fact that it's their responsibility and mom is not a maid. My own fault!
So those of you with small children or grandchildren, take my advice. Train the kids to do their own cleanup. It not only teaches them responsibility, but it will also help you in the long run.