These are a few shots of how I determine and place carved writing on pottery. With bowls or plates, when the writing will be along the circumference of the piece, I measure the diameter of the circlular opening and multiply this by 3. So, if a plate is 10" across, I'll have about 30" for the type. This little gem of geometry (pardon me if it is really algebra, it's been a long time) was something I took home from the Hayes Bayless workshop. I'm sure my high school math teacher would say that was required knowledge to pass their course, but I had certainly forgotten it until reminded by Mr. Bayless. You can also use a handy sewing measuring tape to get a rough figure if you forget the formula!
Once I have the space, I go to the computer and enlarge the type until I get the size needed for the circumference and print it.
At this point you could cut and angle the pieces and trace the writing on the plate using a dull pencil for the outline. I prefer to wing it, and just use the visual length of the words to keep me in the ballpark, making minor adjustments as I go.
This type face was American Unical (no caps in the typeface, so you have to do all lowercase or make up a reasonable substitution using your imagination and those years spent perfecting the alphabet in second to fourth grade).
I'll try and post images of the finished pieces when glaze fired.