Soft shadows can do a lot for creating realism. Take a look at this tutorial by Necati Pamuk for simulating radiosity. http://www.bryceanworlds.com/pages/simulated_radiosity1.html Rubycon

It's harder to make an object look realistic when it's in a plain enviroment. Since your mug is reflective, it would look better if it was on a table with other objects to reflect. There is also lighting. Almost no lighting is purly white, especially interior lights. Don't forget stuff like steam coming off the coffee, and if you can; lip and/or fingerprints on the cup, coffee ring on the desk, etc.

thanks rubycon that link is very helpful

Looks better already. The lighting off the top of the liquid also improved. You can adjust the sharpness and darkness of the shadows by making the light dome larger or smaller. Putting a texture on the table will help hide those shadow lines. The more lights you use the better the shadows, but the longer the render times. Rubycon