I think the basic shutter speed to be used for blur free images isn't as fixed as 1/500s.
That's a bit extreme when using a 24mm lens!

Just keep it to a minimum 1/focal length at least .. and maybe just a touch faster if you're still having issues.

I just did a quick test/play and can get 1/20s-1/15s and sharp shots from the 24-70VC @ 70mm, with the VC on, but it goes to mush at 1/10s and below(zero sharp images out of 6 shot).

image stabilisation is a feature to have high up on your list of usage or next purchases with the D800.

if on tripod and images are still blurry, could be either an inadequate support setup, incorrect usage in some way, or just plain ol mirror slap.

Even with all this, I think the lens used(for these unsharp images) needs to be a priority in any further discussion.

if the lens is a Nikon 24-70/2.8, then technique is going to be your problem. This lens is stellar in it's image rendering ability.
if the lens is a Kipon 1000mm f/11 'drain pipe', then no matter your technique and support gear .. your images will be pretty much unsharp!