Time to get ruthless.
When buying electronics, download the manual and store it in the cloud.
If you're positive you won't be returning it, you can safely discard the manual. Uploading an electronic copy to the virtual cloud of your choice keeps you covered in case the manufacturer stops producing the item and takes the manual down from their site.
Read more here about archiving your manuals into iBooks (if you have an iPad).
Enlist the rule of five every time you clean.
Whenever you're cleaning a room, get rid of at least five items, whether it's a piece of trash, an old magazine, or just something you haven't used in ages.