Details that are never seen but needed for believability. This is my first product render of this kind, and the flask were modeled by me in Bergen, thats why it is Made in Bergen

Reference images handed over from Metric - I often do this part my self, but they had a direction they wanted.

Light setup is based on one huge softbox in the back and two in the front
 

Here's a sphere representing the light setup

To get a realistic room feeling I made a HDRi of my office briefroom. You gain details you'll never can plan for
 otherwise.

 Bottle blue prints from Bruni Glass

I guess this isn't totally physical correct, but if it works it works. There's no specular in the liquid of instance.
In Arnold Render you have the abilities to add Dispersion and Caustics that adds a lot of nice micro details.