I pondered these questions as I began work on my 2015 Challenge piece for the International Freeform Fiberart Guild - a Yahoo group with affliate versions on Ravelry and Facebook. (Here's the link for the 2013 challenge, 2012 and previous, and 2014.) My Challenge pieces have been types of work that I've not done before; new stitches, new combinations, new inspiration, NEW. I like new, but, if you know me, you already know that. This year will be no different in that respect.
So, when Mama Jude of Mama Jude's Plant Dyed Stuff showed me the big hank of thick and thin blue yarn, I was excited to try this type of yarn. The sections are short, and I tried a swatch crocheting only the thin sections leaving the thick sections in great loops. It was beautiful but not what seems right for the 2015 theme: Ocean - the color of water. So, I changed to a size 30 hook and did some single crochet with it. Nix on that. Finally the size 15 knitting needles felt right, and I began a 30 stitch cast-on; after 20 stitches, I stopped and knit one row. Nice, but not quite right.
Back to Ravelry to look at uses of thick 'n thin yarn. The stitches used in By Day, By Night scarf are interesting, and I've used them twice, but wait. My So-Called Scarf (found on Ravelry but the link doesn't work) produces a herringbone-like appearance; perhaps that will work. Ahhhhh. Slip one, knit one, PSSO. Answer phone. Where was I? Oops. Not there. Dang. dropped that stitch.
The herringbone stitch pattern pulls the yarn in so that my 20 stitches were suddenly 10 stitches short of my goal. After five rows and five interruptions, I decide that is a good look. But I also liked the crocheted shell pattern that I saw; maybe I should try it. Transition from knitting to crocheting and proceed with double crochet shells.

(Note photographs and specific discussions of the work itself are deferred to post publication in June.)