The main idea here is that rather than a spine of yo k1 yo, you move all the overs to a single row every 6 or 8 rows. You could do this for any shape of shawl, not just crescent. The nice thing about starting this way is you (should) be able to avoid the hump that crescent shawls often have. Start with a garter tab, pick up 9, left stitch is the center.
Shown with a cast-on count of 7 stitches.