This will be a short but perhaps useful technique for cutting glass. Forget the glass cutter or the pliers.

You will need
1 A hot wire cutter
2 plate glass
3 a sheet of aluminum foil
4 a pan of very cold water

Start by laying a sheet of aluminum foil on an insulated surface. it should be as wide as the area you want to cut on the glass.

Lay the glass down flat against the aluminum foil
place the hot wire cutter wire on the line you wish to cut on the glass

Turn on the hot wire cutter and let it heat up and heat the glass.

After one minute of heating (time depends on glas thickness) remove the hot wire and dunk the glass quickly but uniformly into the cold water.

When the glass panel is inserted into the cold water the area thats been heated needs to enter the water all at the same time. The change in temperature causes internal forces of contraction to snap the glass instantly. Its wierd but it works.

The glass will break exactly on the line of the hot wire cutter.

Caution always be carefull of sharp edges and the proximity of water to electricity.

Step 1: The Setup

Arrange your work area in a way to give you unrestricted movement from the heating area to the water trough. You'll have to move quickly and precisely.

Step 2: Heating With the Wire Cutter

If you are cutting regular glass, a sheet of aluminum foil will insure more even heating from the hot wire to the glass. its not neccessary with a mirror. the reflective layer on the mirror acts in the same way as the aluminum foil. With a mirror it may be neccessary to score the plastic coating on the other side if the glass to insure a clean separation

Step 3: Snap!

Thats what you should hear as you quickly insert the glass evenly across the heated area into the cold water. Use very cold, almost freeezing water. I apolgize for the picture, but thats what it should look like.
The heated line of the glass should enter the water all at the same time.