I'm a couple of days late and more than a couple of dollars short but here's my 2 cents worth anyway.
Choose two yarns that you have either used, are in your stash or which you yearn after and capture what it is you love or loathe about them.
I had some angora that I loved. It's generally beyond my budget but I bought the brown to line some mittens per the instructions of Anna Zilboorg in her book Magnificent Mittens. I've made several of these mittens over the years and learned so much from making them.
I pulled this picture out of my pre-Ravelry actual, physical scrapbook. I gave this pair to my Mom for Christmas one year lined with angora. Yum yum.
Angora, soft and gentle. Not just soft but I think it may caress you back. So soft. I love angora.
Yarn #2 is one I really don't care for. Now, I know I just extolled the virtues of a rather expensive yarn but I'm no yarn snob. I'll use acrylic when needed and have a small stash of acrylic favorites that I get when they're on sale so I'll have them around for emergency baby/kid gifts and things like that. I'm especially fond of Lion Brand Homespun, Bernat Satin Sport and Caron Simply Soft. They wash really well, have some good colors and feel just fine to snuggle with and to knit with. So one day I took a chance on some Bernat Camouflage Ombre. It was horrible. It hurt my hands. It stuck to the needles. It was ugly. My daughter loves it. Who's to say, right? Not all wool is great to work with and not all acrylic is great to work with. I wouldn't turn down ANY angora though.