I read the Marie Kondo books one after the other and began working my way through the house one room each month, throwing away, recycling and rehoming pretty much everything useless.
The main thing for me is less stuff; we have two DCs and huge families and lots of close friends so christmas and birthdays are overrun with stuff, so much that they can't even work their way through it. So we cut that down and when anyone asked what they wanted, we'd suggest day trips, cinema trips, swimming pool trips, anything that took their fancy but which didn't add to the 'stuff' quota. The other thing I do is go through everything before going to bed; pe kits, lunch boxes, school bags, my work bags, everything si packed, clean and ready for the following day.
And get help. Don't do everything yourself. If you have a DP?DCs or friends who'll help, rope them in and get them sorting through stuff. Our local DV hostel is always so grateful for children's books, toys and clothes, unused toiletries and clothes for women. Some arrive with very little and anything lounging about in a wardrobe has got to be better off being worn, so I have clear outs regularly. Our local children's hospital and our GP also regularly need toys and books, so check if anywhere near to you needs anything you have too much of.
At our local tip they take in electrical goods to repair, too, so get rid of all your old stuff that way.