1. Give Away
Throw away the trash. Box up the storage items. Box up your donation and sales items. Only put the keep items back in their proper places.
Accomplishing one small area of your home can give yourself the confidence to do more. Try to make your decisions quickly and you will be less likely to hang on to something you don't need. Make sure to maintain the organization of that one clutter free space. Become protective of the areas you've organized. Refuse to let them become reinfected with clutter.