@unknownuser said:

How i can to obtain a white floor with a mirror effect?

In attach a simple jpg: a white floor with a mirror effect using only SketchUp.
A good tutorial:
http://forums.sketchucation.com/viewtopic.php?f=22&t=4721
or wonderful examples:
http://forums.sketchucation.com/viewtopic.php?f=81&t=17265&st=0&sk=t&sd=a&start=15
For other effects you must use a rendering software as explained in the previous reply posts.

Eli

SketchUp.jpg