I am lucky enough to have a sewing room which is currently undergoing a major cleaning and reorganizing effort, I've been lazy and haven't done it for about 5 years so I have a lot of disorganization to fix. It's the smallest bedroom we have, less than 10x12'. Unfortunately for me, the closet holds long term storage non-quilting items I'm not willing to give up yet, like a full sized Jenny Lind spool bed that's been in the family for decades, my/my son's cradle, sleeping bags and other things, it would otherwise hold most of my fabrics. Instead of the closet, I have two rolling wire rack Costco storage units, a large bookcase (not all quilting related), a desk, a sewing table, and a small non-moving set of shelves. I have taken some "before" pictures, when I get done I will take some "after" shots. There is so much storage when the ironing board is set up there isn't much room, basically a clear path from the door to the wall that goes between the desk and table.
I mostly work with scrap quilt so most of my stash are small pieces (typically under 1 yard). Plus I've been quilting since 1978 so I've accumulated a lot of fabric. I used to keep my scraps in a hamper and that worked well enough for awhile... but it wasn't pleasant going through the hamper -- I had to dump everything out every time and it was lumpy and and tangled and everything always needed ironing so I decided I needed to do something better.
First thing I did was decide I didn't have to save every single piece of fabric. If you are going to make a string quilt, fine, put the long ragged ends in a box specifically for that. Me, I decided that 6" was really what I wanted to keep (I've changed my mind to 6.5 as being more useful), although I will save trimmed WOF lengths in 4.5", 3.5" and down to 2.5". When the yardage gets low it gets cut into the largest strip size possible. The strips I keep sized sorted and roughly colored sorted in a box specifically for them. Cut and stacked neatly they take up much less space than they did in the hamper. When I start a project, I go to the strips first.
Larger pieces of fabric are kept in color or themed sorted boxes, including fat quarters. Because I'm behind on my quilting and because what I really love to do is piecing, I have two large clear plastic tubs with unfinished tops, combined with their backs and bindings. One large tub of "pieces big enough for backs" that don't have tops yet.
Because of my style of quilting (typically using charms or no more than 4 of any given fabric), it often takes considerable time to collect enough pieces so I have small project boxes. For instance I am just about done cutting fan blades for a Thanksgiving themed fan quilt. Another box has my "postcard" quilt pieces together (i think after my recent trip I might just have enough!).
If you work in an office (or know someone who does) the "paper boxes" (cartons reams of paper come in) are a lovely size, not too big/not too small, and sturdy enough to stack 4 to even 5 high. I know a lot of people like clear storage but my fabric may indeed sit for years so I like the light protection cardboard offers, I line the boxes with acid free tissue paper. Note: you should NOT store cardboard boxes on a cement floor, moisture will wick in. Now that I no longer work I buy the heavy duty (light weight is not enough) office file storage boxes.
I also offer charms to people wanting specific things, post here or send me a private message. I have a number of themes/novelty fabrics as well as more standard fabrics. It can be nice to get stored fabric from someone like me because it isn't what is out in the stores that you can find yourself. This is a sincere offer! I really am trying to not buy new fabric (not with much success...) Since I was diagnosed with my vision issues a few years ago I have already given away about 9 full black plastic garbage bags of fabric.