Start with the room in your house that has the most clutter. Place two boxes on the floor in the center of the room, one for items that can be recycled and one for items to donate to charity. Work your way around the room, deciding what to do with each item. Be ruthless; don't keep a shelf full of books that you are not going to read again. Get rid of CDs and DVDs that you will not watch again. Give these items to charity and free up space in your home. Fill a trash bag with things that are old and beyond repair. Hold onto items only if you love them or use them on a regular basis.
Work your way around your house, repeating the same process in each room. Throw out broken items, such as old children's toys, and toiletries and cosmetics that are past their use-by date. Sort through each family member's closet, taking out all garments that have not been worn in 12 months. If you have not worn something for this length of time, you are unlikely to wear it again. Don't keep things out of nostalgia; they are taking up precious storage space.
Look at the furniture in your home after you have removed all unwanted items. If you have removed a large quantity of books, CDs, magazines, etc., you will probably find that you have a few items of furniture sitting empty. Get rid of surplus bookcases, CD racks and magazine racks; if you don't, you will end up filling them again and the same level of clutter will creep back into your space.
Cut down on the amount of paper you have piling up on your desk or in drawers by shredding junk mail, old correspondence and paid bills. Scan important documents that you need to keep and save them in a file on your computer.