Garter Tab Cast On
The Garter Tab Cast On is often used in crescent shawls and other shapes that begin with a small number of stitches and grows outward as the pattern is worked.
You begin with a small number of stitches, knit a few rows, and then pick up stitches so that you have live stitches on all but one long edge of your garter stitch tab. The pattern will tell you how many stitches to cast on, rows to knit, and stitches to pick up.
The following video demonstrates the basic Garter Tab Cast On technique: