Blender 3D: Noob to Pro/Every Material Known to Man/Glass

This tutorial is created more than 4 year ago,so it MAY contain outdated interface

Important things to know about Glass

Glass will not look transparent (outside of the materials panel) while you're looking at it in Blender! It will only look like glass when you render (ray trace) the model.
Glass needs light coming from different directions, in order to look transparent, start with 4 lamps equally spaced around the glass area in order to fully see the effect, then add/remove lamps to get the effect you are looking for.
In versions of Blender 2.37 and lower, don't forget to enable raytracing on the render tab (Press F10 in the buttons window, then go to render tab within that window and click the button Ray which will enable the raytracing). (This setting only applies on rendering while using Blender Internal, not suitable for others like Yafray, etc.)

Simple Glass

Material
Alpha: .2
Color: a color of your choice ( try and keep the S(aturation) below .6, for best results )

Mirror Tran
Ray Transparency: enabled

Realistic Glass

Material
Alpha: 0.1
Color: White (hex code: FFFFFF)

Shaders
Reflectivity: 0.2
Specularity: 1.5
Hardness: 511
Translucency: 0.5
Ambient: 0.5
Emit: 0

Mirror Trasp
Ray Mirror: enabled
Ray Mirror: 0.2
Ray Transparency: enabled
IOR (angular index of refraction): 1.37
NOTE: it is suggested to play with the Fresnel for transparency.

Note: Don't forget to enable raytracing on the render tab (Press F10 in the buttons window, then go to render tab within that window and click the button Ray which will enable the raytracing). Raytracing is enabled by default in Blender 2.37 and higher. (This setting only applies on rendering while using Blender Internal, not suitable for others like Yafray.)

Mirror Glass

Here is an example of some glass that is less transparent and more reflective, almost a mirror. Just play with the "Alpha" setting until you get the effect you want.

Material
Alpha: .2
Diffuse Color: R .74, G .776, B .818
Speclular Color: R .676, G .732, B .798

Shaders
Diffuse Shader: Oren-Nayar
Reflection (Oren-Nayar): .959
Roughness (Oren-Nayar): .818

Specular Shader: Blinn
Specularity (Blinn): .731
Hardness(Blinn): 179
Refraction (Blinn): 10

Mirror Trasp
Ray Mirror: enabled
Ray Mirror: .56
Ztransp: enabled (this is very important, otherwise when you set your alpha value, only your background color will show through, not the object behind the alphaed object)

All the rules for raytracing apply as written above.

Plate Glass with green edges

Another glass setting. This one even has green edges by having different materials for them.

Glass with green edges: Click to enlarge

The Ztransp button should also be enabled, to allow the glass to show the material behind it.

Apply the green edges by using this material for the edges: