…I’d start with detailed measurements and a floor plan.
But of course, I don’t have a floor plan, and the most detailed measurement I have is a hastily scrawled “8.5′ x 11′, closet door on short side, door to hallway on long side”. That’s not enough for detailed planning.
It is, however, enough for me to start fiddling with. Last time I designed my studio, I used Photoshop:

That worked out okay, but it had a kluge-y air about it. Photoshop wasn’t really meant for this kind of layout.
However, in the interim, I have acquired Visio, which has all sorts of templates, including several meant for laying out home plans!
So I have whipped up a mockup of an 8.5 x 11′ room with two doors:

I have actually not used the full power of Visio; if you want to get fancy, you can put in little potted plants, sofas, and other things too cutesie for words. However, since virtually everything I’m adding is a rectangle, I just used a “table” template for everything but the dress form.
Notice there is no loom in this simulation. That’s because the loom is going into the garage. The new studio is considerably smaller than my current one, and there’s just no space for the loom. Also, it will be quieter in the house if I weave in the garage. So, of course, I will need to do the garage floor plan, later.
Anyway, the preliminary results look promising. It will be a tight squeeze, of course, but in a pinch I can move the storage shelf out to the garage, or put the contents into the closet, which should leave plenty of space for the bookshelves and work areas. I’m already thinking about expanding the work table to the full length of the wall (to make cutting yardage easier).
Tomorrow is the final inspection (plumbing specialist), and I plan to take the opportunity to develop a more detailed floor plan for the room (this time actually finding out which ways the doors open and where on the wall they are!). After that I’ll arrange the virtual furniture until I arrive at my new studio design!