I agree that the cable needs to be supported along at least part of the handlebar. I have seen pics where the cable is wrapped up to the point where the bars start to rise, but I typically route the cable along and up the bars until the brake hood. At the hood, I place the cable to the inside of the bar, where it has a nice short and clean route to the down tube bosses. The benefit of this is that it is a "natural" place for the cable to escape from the bar tape.

I do what 79pmooney does to wrap bar tape, for exactly the same reason. Another hint: put the beginning end of the tape next to the cable where it exits the shifter, with the tape roll pointing to the inside of the bike. I have found that going in that direction first seems to make the rest of the taping go more easily.