The garter tab is a common method used for casting on shawls.
Once worked it will form the centre top line of the shawl. Increases are then worked in the pattern to create the shawl shaping
1. Make a slipknot and slide this onto the right hand needle, gently pulling the yarn to tighten
2. Using a long-tail cast on, loosely cast on 3 stitches
Handy tip: at this point I like to thread a piece of scrap yarn through these stitches as it helps when picking them back up at the end
3. Knit 6 rows but do not turn the work after the last row. Turn the work 90 degrees clockwise