I did this scarf in a roundi-round fashion, like they make braided rugs. I just kept going around the ends, never turning and heading back in the direction from which I'd come. So the ends of the scarf are round too.
As I got nearer to the end of my skein I stopped and found the other end of the yarn at the center of the skein. Using that end I finished up the hat. That way I knew how much would be left to put on the scarf. I certainly didn't want to finish the scarf and not leave enough for the hat!
Now they are both looking good!