First, determine HOW MUCH SPACE YOU REALLY NEED AND ACTUALLY USE! This is not, "one day I might need"..... or "when company comes over I could use the"...... or "when Mom comes to visit she can stay"........ or "I might host the Holidays this year"!!! Nope! Each day, every day, what do you use and where do you live? When I paid attention to the idea of down sizing, I found that my daughter and I really only used the master bedroom (co-sleep), master bathroom, living room, and kitchen. Her room on occasion we played in but usually toys found their way to the common area to be enjoyed. So, that meant that we could eliminate the 3rd bedroom entirely, the entry/foyer/dining room, a part of her room and a bathroom. Not too bad! This also meant I would have less to maintain, upkeep, store, and furnish. Conceivably, we could live quite comfortably in about 800 - 900 square feet if it was laid out correctly. Duly noted!
Second, determine WHAT STUFF YOU USE EACH DAY AND WHAT STUFF YOU ARE PAYING TO STORE. This, like the above, is easily done in a week or two if you pay attention. If you are serious about down sizing, get active and get some boxes. Label one "donations", the other "recycle" and the last one "garbage". Hopefully the garbage has only a few unidentified chewed on toys and a sock or two and that is all. Green eco-living remember!! Most everything can be reused or recycled somewhere!! I promise to make a list of places and ideas and links to help with this a.s.a.p.! Put the boxes out of the way but accessible enough for you to be able to toss stuff as you come across it. Then, start purging!
Rule 1: If you haven't used or worn something in 30-60 days, donate it. The exception to this is off-season clothes and anything you do use but the need is only every few months (example, hair coloring products or hair cutting scissors, or ink toner or wite out). Stop storing crap you are not using, its hoarding, bad karma, stuck energy, and weighs down your house and your soul. There is a great story of the monk who goes out each morning with his begging bowl empty and returns each night with it full. If he went out again the next morning with the bowl full from the prior days gifts he couldn't receive today's. So, consider the idea that you too can not receive any new gifts from the universe if you are currently full up and over flowing with stuff you don't even use, need, or remember, but refuse to empty. Let it go (try not to sing the Frozen tune here) and let new come in to your life. Besides, my personal theory is that if you are holding on to something you do not use, shoved somewhere you can't even get to, it isn't yours and you are keeping it from the person it truly belongs to. They are waiting for it so put it back (recycle / donate) into the flow and allow what is yours to come to you. I can not tell you how many times I cleaned out my house, donated, and had something provided to me that I had been waiting for (a new lamp on the side of the road --- no I did not have to dumpster dive for it --- that I really needed because mine got knocked over). I believe stuff has energy and when you keep it or hoard it, you stop the ebb and flow to you! (I believe this about money too but more on that later!)
Rule 2: Only so much fits so determine what percent must go and what percent can stay in order to properly take up residency in your organized zen home! Look at your home, take it all out mentally, what percent or amount would you put back in to keep a peaceful, green, organized zen home?? 10%?? 25%??? 50%?? What ever the number is you now know the number that must GO. So apply the procedure above with the knowledge that only so much can stay. If it helps and you can, actually take the stuff out. When I organize professionally, this is my approach. People are AMAZED at what possessions they own when you lay it out before them literally---shocked and embarrassed too! It is a great technique if you can physically and emotionally do it. Take it all out, look at your space, determine how you want it to be and feel, put back only the items you use, need, and are willing to use good resources to store and maintain.
Respect and honor the feeling of purging and lightening and don't put back anything that tips the scales back to excessive. Give it a try......clean, donate, reduce. recycle, purge, and let me know how it feels!!!!