>Any professional experienced with the D800 who can give some >tips?
How about an amatuer?
Besides the good advice already given, I would start by getting a baseline of "sharp" with each (or at least one one of) the lenses.
Put it on a sturdy tripod, outside or in very bright light, and use Live View zoomed ALL the way in with auto-focus off, shoot at a very fast shutter speed, and see what you get. Do it a couple times just to make sure. This should be focused as good as it gets, and with a very fast shutter speed have no motion blur (turn off VR if those lenses have it).
Now shot the same in the same place but with auto-focus on (and live view off). Do this a couple times.
If the latter is not as good as the former, start adjusting fine tune.
If they are the same, and you are not happy how sharp, make sure your expectations are reasonable. Compare to the same shot with the D200 (perhaps post some). Sharpness is not really the same as resolving power of the additional resolution -- sharpness is more of a post processing feature for edge contrast. What you can resolve is more about the additional pixels. Try compare with minimal sharpening added, and look at fine detail, it might give a clue as to whether you are seeing a contrast issue. Or a CA issue. Maybe post some samples.
I'd guess either your expectations are exaggerated or you have a fine tune issue.