Try this. Whenever you bring new items into your home to keep, eliminate the same number of items you brought home, plus one. So, for example, if you bring home 15 items from the grocery store, get rid of 16 items. Don't forget to count the receipt as one item if it's something you'll keep. Little things like that can add up.
To get rid of items toss them in the trash, recycle them, or put them in a box for donation. Remember to actually take that box to donate somewhere when it's full. ;) By eliminating the same number of items you brought home, plus one, you will always end up with less than what you had before. You may even end up finding more items to get rid of. Just be sure it doesn't take up so much time that you neglect other things that you want to get done. Set a timer if that helps. It's a good way to "schedule" time to declutter without taking up a huge chunk of time. Another benefit to this strategy is that you may even start buying less because the more you buy the more you have to remove from your home. Try it and let me know if it works for you!