When I'm in the middle of a project I do not put things away. They stay within reach as needed. When finished with the project everything is tidied up. I look at it as washing the dishes. Rulers, scissors, pins, patterns, etc. are put away.
Scraps are dealt with and assigned and cut to specification of future scrap quilts. I always have a scrap pattern in mind for them and there may be several patterns. It helps with the storing and cutting and taking care of scraps.
I make scrappy quilts when the scraps I have cut fill their designated storage container and I have enough to make a quilt. I buy new fabric to help finish what I've started. My stash is rather large and I find most of the time something will work from it.
I have ufo's in separate plastic containers which are stackable. I allow myself to start something new if I've finished a ufo or a scrap quilt. My ufo's are dwindling but I still have a lot of them.
If I have several wips and working on all of them at the same time they stay in or are put back into their storage boxes as I finish whatever part I'm working on until next time.
This has worked for me and things are not as messy. Good luck to all of us as we conquer our creative messes!