okay basically what happens a lot of times when we first start learning to knit is that when we turn the needles the yarn is in front (if you are doing knit stitches). When you move it to the back you have to be sure to pull it under and behind the needles. If you pull it OVER and behind it will make it look like there is another stitch there to knit thus increasing your stitches. i would suggest going ahead and casting on about 20 stitches or so and just knitting away. Count the stitches every few rows to see that you still have the number you started with. I would stitch it until it is about 5 feet long or so and you will have knitted yourself your first scarf AND got a whole bunch of practice just in knit stitches. You will see how your tension changes from the beginning to the end too.