I have just finished another baby cocoon. I use a standard beanie pattern starting from the bottom with a majic circle and put 12 double crochets into it. I do 2 dc per stitch on the second row ( 24 sts) , and the third row is 2 dc's every other stitch (36), fourth row is 2dc, dc, dc, and repeat(48 sts), fifth row and usually my last row I do 2 dc, dc, dc, dc, and repeat for (60sts). If you use #4 or #5 yarn that is perfect. I use a J or K hook, depending which one gives the texture I want.
I dc until the total bag is 16 inches or so, all worked from the front, then I do a contrast yarn sometimes, and turn my work (so it folds over nicely) and do 5 or 6 rows of single, half double, or double crochet, OR pick up stitches and knit a ribbing like I did here of Knit 1 Purl 1 ribbing. ( I didn't turn for the ribbing on this picture, I liked the looks of it done on the right side) then bind off.Attachment 16584