These two stitches are the most important parts of knitting. The knit stitch is of obvious importance, given the naming choice. In stockinette stitch, the knit side looks like columns of interlocking vs, each v being one knit stitch. When you work with straight needles, you will need to turn your work at the end of each row. In order to keep the knit stitches on one side of your work, you will need to purl. This is nifty because a purl stitch is a knit stitch from the back of the fabric. Not to be confused with a tink stitch, which is simply what you do when you must knit backwards to a booboo.
Step 1: Cast on your stitches
I like to use a long-tail cast on. I have an instructable that can help you cast on 15 stitches for a cable swatch that I am making. By whatever means you choose, cast on 15 stitches.