Hold the tail end of your yarn in your left hand, together with one needle and the working yarn in your right hand.
With your right thumb, place your thumb over the yarn between your two hands, tuck it down behind the yarn and bring it up to the front. You now have a loop on your thumb, with the left needle, place the point of the needle to the right of this loop and slip the loop off your thumb. You now have one stitch on your left needle. repeat the process until you have enough stitches on your needle. This is not one of the best cast ons but it is sometimes useful if you need to cast on a couple of sts at the end of a row or you want a few sts to try out a piece of a tricky pattern as a sample.