Tip #1: Don't buy the storage containers to organize a space until after you're well into the sorting and tossing of your things.
Many people go out and buy all kinds of tubs, boxes, baskets, and bowls to organize a space. Don't do it. Wait until you get the space you are working on cleared out, sorted through your stuff, and when you have what you know you're keeping, you'll know what you need to store it in. You'll also have a better understanding of the space you are organizing, it's easy to think it's bigger or smaller after looking at it jam-packed for years. This way, you won't have stuff you can't use, and have to buy the storage containers you actually need.