I found this pattern in the general forum my question is : Should I decrease only on a purl row and then knit the next row as is?
Cast on 90 stiches
Rib: 1x1 rib for 1 1/2 inches: 1k, 1p to end -- start each row with a knit and end each row with a purl so you stay on track.
Body: Stockinette stitch for 3 1/2 inches: k one row, p next row
(put whatever kind of pattern you like here, I use this site to create a chart for this guage and sketched out the logo you see above)
k2tog, *8k, k2tog repeat from * to end
k2tog, *7k, k2tog repeat from * to end
k2tog, *6k, k2tog repeat from * to end
continue in this fashion until 10 to 15 stiches remain (you'll see that the decreased stitches line up to form nice "darted" lines in the hat)
cut the yarn, leaving a 24 inch tail. Thread the tail through the remaining stitches and use to sew up back of the hat.