Things have a place.
I don't keep letters unless it's documents that are needed and then we have file boxes with a system for things like that.
I have a cupboard in the kitchen for bits like vases and candle holders that I might get out for special occasions.
We have bookshelves for books.
A coat cupboard under the stairs for coats and shoes, with some drawers for hats, gloves and scarves. School bags and shopping bags hang in there as well. Wellies and walking boots are on a rack in the garage. Oversized coats in the wardrobe in the spare room.
Cleaning products are stored in bathroom cupboards or the utility room.
Camping stuff and tools in the garage. Xmas Dec's also on racks in the garage.
Bikes and garden tools in the shed.
We have a couple of boxes with memory bits in e.g. first babygro's / shoes / photo album stored in the loft.
Kids mostly keep their stuff in their rooms. Family games in the sideboard.
Bed linen and spare towels in the airing cupboard. Spare duvets and pillows vacuum packed and stored in the spare room ottoman bed.
Kitchen appliances, food, crockery etc all in the kitchen.
I have lots of craft stuff which is also stored in the spare room in a cupboard next to the desk I use.
The key is to regularly get rid of things you have no use for and to find storage for the things you do use.