Just have an established number of bins or containers, or whatever your preferred method of storage is, and here's the key: DON'T buy any more containers. Your child's toys must continue to fit in those containers.
1) You'll think really long and hard before you buy a toy because you have assigned yourself a limited space.
2) You'll be more likely to purge toys that aren't played with or don't inspire creativity to make room for new toys.
3) You can box up the toys that are no longer age appropriate for a future child, or you can save a chosen few for keepsakes, and donate the rest.
When it comes to getting organized, what you need really isn't more containers. It's less, more carefully edited, stuff.
(Image: Kalon Studios via Branch Home)