If you're using circular needles in the round with the ends joined into a circle, you'll just knit all around on every row. That automatically makes stockinette and you don't have to turn it or purl. It sounds like you're using a circular needle like you would regular ones and knitting back and forth. Then you'll knit the right side rows and purl the wrong side row. Your knit stitch will look like little V's. Your purl stitches will look like the neck on a turtle neck sweater. That's how you tell them apart. Knitting is generally done on the right side rows and purling on the wrong side rows. It's easy to figure out whether you're on a right or a wrong side row. If you're following a pattern, your odd numbered rows will be your right side rows and your even numbered rows will be your wrong side rows. Most of the time, unless you have a special cast on, your tail will be on the right when you're on a right side (knit) row and the tail will be on the left if you're on a wrong (or purl) side row. Hope this helps you.