I just got done screwing with my 2 6000's in my tank and found that having them as high up as I could put them, facing each other and dialed down some, gave me a good flow in the tank, that my LPS could live with, but still have enough flow to keep things stirred up and in the water column.
So, if you only have one, I would pick a side and place it as high as you can and place it as close to the front glass as possible, shooting water longways across the tank, but have it angled towards the middle of the opposite side glass. So instead of it being parallel to the front glass, it would have like maybe a 30 degree angle back towards the back glass.
This will give you flow across the majority of the tank, along with alot of surface agitation to promote gas exchange and not let gunk accumulate on the surface and also provide good deflections of flow off of the opposing glass.
Try it out and see what happens.
Best thing you can do is trial and error. There's no right or wrong, just what works and doesn't work in YOUR tank.
Good luck.