Why do you keep adding an extra stitch when knitting?

you are probably not picking the stitch up in the right spot so you are getting lets say 1/2 the stitch and then again getting 1/2 again .. but you you only do it sometimes.. when you learn to knit stay to the points of your needles at first to make it clearer to see the stitch .. chances are you are doing this at the first stitch when you turn