How do you form the crown decrease rows when knitting a hat in rib k1p1 stitch?

When you reach a purl stitch approximately where you want to make your decrease, knit it together with the following knit stitch. This will make two knit stitches in a row, followed by a single purl. Place a marker and move to the next place to decrease and repeat. If you consistently knit together the last two stitches before your markers, you will form an attractive pattern in the ribs as you decrease.