Make a loop in the yarn. Make another loop and pull it through this loop. Pull the slipknot tight.

You can make a small sample square of one inch to determine the number of stitches you should have. The number of stitches depends on the size of yarn you are using. For instance, a bulky or sport weight yarn will have fewer stitches than a fingering weight yarn. Another factor is tension or how tight or loose your stitches are when you knit.