This is the first in a series of basic crochet stitches. In order to start almost any crochet project you have to make a slip knot, so that's where my series is starting. A slip knot isn't really a stitch so most patterns don't even tell you to make one. You just need a slip knot in order to make your first real stitch.
To make a slip knot, make a loop in your yarn and put the crochet hook through the loop.