I remember knitting my first shawl and it calling for a garter tab cast on and being totally confused by what this meant. Once a friend showed me how to do it, it was so simple. Since a lot of my shawl patterns call for a garter tab cast on I thought I would put a short photo tutorial here.
First cast on 3 stitches and knit 6 rows
Rotate work onto its side. Pick up and knit the 3 ridges (bumps) along the side of the garter rows
You will now have 6 stitches on the needle.
Rotate work on its side again so the cast on edge is at the top, pick up and knit 3 stitches from the cast on edge
You should now have 9 stitches on your needle ready to carry on with your shawl