Designing knitting patterns: how do you do it?

Dear users, dear authors,
how do you design a knitting pattern, e.g. for a shawl?
How do you go about it?

It varies for me:

Either I already have the pattern in my head, or it develops practically row by row.

First, I decide whether it should be a rectangular shawl or a triangular one.
Next, I think about the type of pattern: stockinette stitch to bring out the colors; a knit-purl pattern, lace, or a cable pattern.
Of course, a mix of patterns is also possible.

Once I have a general idea, I start knitting and type up the pattern on the computer at the same time.
Before a shawl reaches its final version, I might have to rip it out and rewrite the pattern.

Depending on the pattern, I’ll also add detailed photos.

It varies a lot. If I receive yarn or color specifications, it’s harder than when the yarn speaks to me directly.
Usually I frog it a few times before the final project is finished. 
I usually test patterns with leftover yarn of the same weight to see whether it works,

I have various books with knitting patterns—a lot of them.

When I like a pattern, I pick out a yarn from my stash that I think would go well with it.
First, I knit the pattern as a rectangle or square to see if the pattern and yarn go well together. Then I decide whether to knit the shawl from the top down or from the bottom up.  

After a few rows, I can tell if I like it, if the pattern works with the number of stitches, and I finish the shawl. Very often, it gets put in the UFO box to rest for a while. Usually, when I think the yarn might be a good fit for the next pattern, I unravel it all again. I’ve got quite a large UFO box by now.