One of my very long-time friends recently found out she's going to become a grandmother. The embryo's parents live in New Orleans, so no wooly wear is needed. Hmmm... I think I'll knit a baby blanket.
First job: Find machine washable and dryable yarn that's soft and has good cotton content. (Don't forget blankets take a lot of yarn, so not too expensive would be nice.)
Ooh, Lion Brand Cotton-Ease comes in some nice colors. Don't know what sex Embryo is yet, so let's get green and blue and purple and cream.
Second job: Select a stitch pattern -- remember to try for something two sided.

Browse through all of my stitch dictionaries and decide I liked "Pucker Pattern" the best. Looks like it should be presentable, if not virtually identical on both sides. Besides, of course, I like the weird name.
Third job: Knit a swatch in pattern and measure.
Knit, knit, knit, purl, purl, purl, cable to the front. Ten inches wide, about four inches long. Four stitches per inch on the suggested size 8 needles. Took somewhat less than a quarter of the skein for 40 square inches.
Fourth job: Do the math.
Need more yarn. Job 4B: Back to the store, get another skein each of blue and green. That makes three blue, three green and one each of purple and cream.
Fifth job: Okay Brainiac, you bought the yarn before you had a firm design in mind, so now design for the yarn you already have.
Draw, draw, draw, calculate, calculate, calculate.

Got it. I'll be cutting the blue and green yarn tight, but if I run too low, I can simply make the blankie a wee bit shorter. (Considering as how I've already spent close to $50 on the yarn.)
Sixth job: Knit the thing.
Now there's the hard part...