Featherweight is worked from the top down. Increases are made on every right side row until you are ready to divide the sleeves from the body.
Here is how I made my increases:
M1: lift the bar between the stitch just worked and the stitch you are about to knit from back to front. Then knit through the front of the stitch. One stitch increased.
NOW, for all you perfectionist knitters out there, yes, you can also M1 by lifting the bar from front to back and knitting through the back of the stitch. Depending on which way you lift the bar, the stitch will slant in one direction or another. Here is where I make a confession: I am lazy sometimes. There, I said it! So in the case of this much loved cardi, I worked all my M1's the way I described above.
If you would like to be a more perfect knitter than I, here is some additional help.
For an increased stitch that slants slightly to the left, lift the bar from back to front and knit through the front of the stitch. Work this increase 1 st after the marker.
For an increased stitch that slants slightly to the right, lift the bar from front to back and knit through the back of the stitch. Work this increase 1 st before the marker.
Next tutorial: tips for working sleeves in the round