Put simply, how a yarn over is executed depends on what comes before and after. There are four situations to consider:
1. Knit stitch, YO, knit stitch.
|Bring the yarn from back to front,|
|then simply knit the next stitch. The yarn will automatically create a yarn over on the needle.|
|Take the yarn from front, over the top of the needle to the back and under to the front again.|
|Start by bringing the yarn forward between the needles, then...|
|take it back over the top of the needle and under to the front again.|
This one is so simple it's tricky. It makes an appearance once in each cycle of the Cataraqui chart.