In this video, I'll cover:

-Box-modeling a water glass for proper volumetric refraction.

-Creating and configuring LuxRender volumes in Blender 2.5.

-Using those volumes with the Glass2 material to match up with the aforementioned model.

-Brief overview of render settings.

-BONUS: Sneak peak at LuxRender's future SPPM mode. :)

NOTE: I made a small modeling mistake in this tutorial. I made both a bottom face for the surface tension, and a top face for the water mesh. You only need one of them, so just delete one.

For more on the subject, like texturing the floor and playing with the water color, see blendercookie.com/2011/05/03/rendering-a-liquid-filled-glass-in-luxrender/