How do you get the best rendering result for a 'mirror like' surface, or a watersurface rendered in rhino?
I reckon that you have flamingo installed. It is like real life: Choose the material properties with a highly reflective material. This can be polished steel for example. But also "car paint" settings can create ineresting mirroring reflections. You can next play with settings of your respective material to 'fine-tune' the effect. Setting some lights also helps to create reflection effects.
Water surfaces: There are a few basic settings as plug-ins. But no-one prevents you from altering those for your own needs: open the menu and try some individual settings.
If you use version 5 of Rhinoceros you have a pretty nice rendering environment: check this video to have an introduction to its use, with mirror and water examples
Here you can download the file I used to produce the video clip:
Tutorial: water material in the Rhino rendering module