Null objects are just solids in disquise. You can adjust their anchor point as you would with any other layer, eitehr numerically or with the pan behind tool. Same for aligning your child/ parent relationship...
I'm not sure I understand your question.
When you create a null, it's centered in the comp. When you make it 3D, its z-value is zero.
When you create a camera, it comes with a position of certain x/y/z values.
How tough can it be to copy the camera's position property to the null's position property, then parent the camera to the null?
The null's anchor point is at the same position as the camera's anchor point. When you move the null, the camera moves.
Is that what you're after?
Thanks guys. I think I had just tinkered with the Anchor Points and Position so much that everything was off. Just reset values and I'm back where I want to be.