This is tip is basically a cheat, since it doesn't actually involve getting rid of anything. But it sure can work wonders for your sanity.
You know those toys scattered across your floor? Behind the couch? EVERYWHERE?
1. Get out a big box.
2. Put every single toy in it.
3. Put the box out of sight. (In the closet, the garage, the trunk of your car, or, if it's a plastic box, your backyard.)
Then, pick 3-5 toys to keep out at a time. Every day or so, swap them out for a few old toys from the box--which suddenly seem exciting and new. In our house, Sam gets bored with however many toys are carpeting the floor, regardless of whether he has 5 out at a time or 50, and he always ends up finding entertainment elsewhere (pulling pans out of kitchen drawers or piles of lint from under the furniture, probably because he prefers real stuff, even lint, to baby stuff).
I told you it was a cheat. But it beats stepping on a Lego at every turn, which is more painful than I can effectively describe.
(This trick can work for grown-up clutter, too, particularly knick knacks, and I've also been trying it with clothes: keeping handy the things I use most, and putting everything else out of sight for a while. And then, when I'm ready for a change, I go "shopping" in my box. Did you ever see that article circulating the web about the idea of putting away every single knick knack in your home in order to clear your head and re-think your decor? Would you ever try that?)