First of all, make sure and use a high quality, brand name coax (i.e. belden etc.). Most pros run the cable
down the roof where intersecting irregularitys occur (like where a front facing surface intersects a side facing surface, or where a dormer window intersects the main part of the house). Most pro installations run the coax in the rain gutters when going side to side (not up and down). I know how this sounds, but I have been told by several companies that this procedure is just fine and protects the cable at the same time! Using these procedures, I have found that the cable is almost invisible. Good Luck!