The easiest would be to make a Blinn material. Make its color white. Turn its Transparency setting up to almost full white.

Now to give it a certain glassy shine, turn the Eccentricity down a tad and bump the Specular Roll Off and Color settings up a bit. You can tone the reflectivity down a tad as well.

For refractions (bending of light in glass/liquids), go to the Raytrace Options and turn on the Refractions checkbox and change the Refractive Index to 1.5 (glass).

If you click the checkered box next to Reflected Color you can create a reflected environment such as Chrome which will give your glass interesting reflections. Or you can choose an image such as a room to reflect in the glass. Or you could actually model the room and place the glass in it, then you would see the actual room reflected in the glass.