Originally Posted by dbakl
On drop bars, they go underneath the drops, wrapped under the tape, and exit below the brake levers each turning inwards towards the centerline of the frame to meet the cable stop mounted about where the downtube shifters would be mounted. The idea is to keep the housing curves gentle and graceful. Don't forget to grease the cables. Of course, modern frames may have other braze on doohickies to help. I don't know what you'd do on moustache bars, something similar?
I would recommend
against greasing the cables, if you're using halfway decent lined housing and slick cables. In this case, grease may actually increase cable friction. That's no fun! Other than that, that's how I route my cables, works great.