Start with a process: reduce, reuse, recycle. It sounds easy, but you have to make difficult decisions. Start with a cupboard and don't try to do everything at once.
Use 3 boxes and tag each one Reduce, Reuse, Recycle and empty the cupboard into the boxes. Make quick decisions. Reduce is getting rid of obvious garbage, bags, boxes, broken items. Once this box is through immediately put it out into the garbage bin. Reuse those items that you want to keep, bedding, towels, kitchen items. Put this box aside. Recycle those items that you would like to donate to charity, friends or family, and give it to them ASAP. Next step - what for the next post.