Mine was oriented with posts set on east and west ends, with the entire length of the panels facing south, to catch the most sun. So, if you don't want to shade plants behind the climbers, set your high plant supports on the north side of your planting space. A northwest corner would probably work nicely as well.
If you plant your seeds or set in your starts on the north side of your support structure, they'll grow out toward the south making them easy to train up. You'll want a walking space available along the south side of your structure to perform maintenance, so I wouldn't make the planted strip any deeper than you can comfortably reach across.
If you haven't yet read it, there's a great article here
http://garden.org/ideas/view/R... that helped me.
