A note on the numbers: For this blanket, I cast on 20 stitches and knit enough rows so that one side had 20 ridges and the other had 19 ridges. I then bound off, making the 20th ridge on the back side. I picked up 20 stitches (some people like to pick up 21 - it's a matter of preference and how tight you knit) and knit 10 ridges. The next time I picked up 30 stitches, and knit 10 ridges. I'm liking the look.
And one piece of advice: weave in the ends as you go. You'll be happier when you are done. Trust me.