Here is my latest project using a combination afghan stitch an single crochet.

I used worst weight yarn and a size K afghan hook.

The pattern:

ch 19

sc in 2nd chain from hook, sc across. 18 sc, turn.

Row 1, The Afghan Stitch:

Insert hook in second sc and draw up a loop. repeat for remaining sc's. 18 loops

YO and remove one loop, * YO and remove two loops* repeat until one loop remains.

Row 2, Single Crochet:

Ch 1, sc around the first "bar" from the afghan stitch and sc in the remaining 17 afghan bars, turn.

Repeat rows one and two for desired scarf length