It boils down to steely nerves.
You start by going into a room and looking at every item in that room. Ask yourself, "What is it? How long has it been there? When is the last time someone used it?"
Then put it into one of two piles: (1) keep it; and (2) remove it.
There. That wasn't so bad, was it? Did you end up with anything in the "Remove it" pile?
If you did, then you are on your way.
After having taken that first brave step, it gets a little complicated
Ask yourself, when looking at the "Don't want it" pile, whether there might be someone else who would like to have it? This part is actually fun, sort of like being "Santa Claus", or "Robin Hood". Is there a special little friend, like a neighbor's child who would really love to have that teddy bear? Would a neighbor like your extra bed that nobody ever sleeps in? How about those old pajamas with clouds all over them. Would they make an entertaining gag gift for a friend? And that bottle of rum that has been sitting in the basement for over twenty years. Time to share it with a neighbor? And all those sweaters that your kids left when they went to college. They boy next door might like that green one.
Now with that list of items in your hand of things you no longer need or want, allow yourself the freedom to divide the "Remove it" pile into smaller, more detailed piles. For example,
REMOVE IT PILE
Pile Number 1. Things to sell.
Pile Number 2. Things to give away.
Pile Number 3. Things to recycle or compost.
Pile Number 4 Things to put in the garbage can.
One way to enlarge the size of the "Remove it" pile is to again look over the things that you already decided to keep the things that you use every day, or every holiday, that you like and want to keep because you need them.
But wait a minute. If you keep looking at that purple vase in the cupboard and realize that you haven't used it in several years, and suspect that you are just clinging to it out of habit, or that if you thought about it, you really don't need it or use it any more because you have two purple vases, then add the vase (or maybe both purple vases) to the "Remove it" pile.
Now we have a new problem on our hands.
What to do with the "Don't Want It or Remove it" pile?
Keep on piling.
Divide the stuff to be removed from the house into smaller, more manageable piles:
Pile Number 1, things to sell, are those items that you really wish you could keep but you don't need them any more like furniture and electrical equipment like radios and stereos, for example, but they are too good to just give away, and besides if you sold them, you could use the profits to get what you actually need. Have a garage sale or work with a consignment shop to get them sold.
Pile Number 2, things to give away, includes all the things you didn't sell at the garage sale, or that the consignment shop wouldn't take, but just couldn't brave up and throw away, but you don't really need and really don't want. It includes old records, books, games, toys, clothing, and other items that you tried to sell at your garage sale but no one bought or took away. Find a friend who wants it and give it to them, of put it in a box on the street with a sign that says "Free" and count the minutes before it disappears.
Pile Number 3, the recycling and composting pile is probably the easiest to identify. It includes broken boxes that would be difficult to reuse, newspapers and magazines, empty wine bottles, extra glass jars, outdated paper calendars, rotting food, and the like.
Pile Number 4 goes to the dump as garbage. It includes all those things that you don't need, can't use, couldn't sell, and that cannot be recycled or composted. Hopefully, it is a small pile.
There now, that didn't hurt a bit, did it? In fact, it was actually fun. Try doing a room per day and see what happens.
But watch out, it gets infectious. Soon you will find the neighbors joining in and adding things to your piles of things to be removed from the house, while they also take some items for themselves from your "give away" piles. Just make sure that you give more than you get.