The boxes are the key of successful organization
So I realized I should find a system that will generally apply to babies and children of all ages. After a long time, and a lot of trying, I realized that the most effective system is the one that includes boxes, preferably those that can be carried with one hand (because your baby is in the other ;)) so you can easily carry things (for example, the outdoor toys). Supermarkets and shops like a Dollar Tree offer a large selection of boxes in various sizes and with various purposes, so it's not hard to find something that would suit you best. If you're like me, and you like to recycle, use something that you already have - like a box of diapers. Personally, I mostly use the boxes in which I have my groceries delivered (ordering groceries online is a great time saving for any mom, but I'll blog about it some other time), because they have holes on both sides and therefore are easily transmitted. If you are uncomfortable with the logo on such boxes, you can wrap it in some gift-wrapping paper (a good idea how to recycle those scraps and wrapping leftovers which you are too sentimental to waste), but I'm not doing it though because I know my kids would tear it fast, so that would be of no use to me.
They are also very useful because they don't have a lid, so in this way a child sees what's in the box, and this makes decluttering easy since you can just pop in things. Of course, the system is most effective when the child cooperates in this chore, but it depends on the child's age, so you can hope to it, some time around the third birthday.
Labels on boxes
In order to make cleaning easy for a child, the labels on the boxes are a great help, especially those with pictures, because then you can use them even with the preschoolers, who still can't read. The tags from this link have been a great help to me.
These labels are sufficiently large and contain a large number of different toys, for the both, girls and boys, so I'm sure that everyone can use them. Of course, I am sure you do not own each type of these toys in sufficient quantity so they would need a box of their own. For example, we keep dolls and Barbies in a single box, common for this two type of toys. Cars, trains and trucks are also in one common box, which means a total of two, not five separate boxes. However, it is better to take pictures of a child's own toys, those which truly are in the boxes, so that a child, especially a younger one, could associatively link a toy and the box itself.
Boxes as a way of cleaning up .... everything!
Of course, the boxes are excellent for organizing the other things in the household, as well. My dear friends lent me some photos of their homes. Isn't it wonderful to open the drawer and immediately know exactly where each thing is? Without tangled necklaces and mismatched earrings! On the photo below you can see a great organizing solution from a friend of mine, which includes a recycled candy box for tiny pieces of jewellery.