Drilling glass has many interesting and useful applications ranging from artsy stained glass work to bong making (see Mrs. Butterbong). There are some important things to understand about drilling holes in glass that differ from drilling metal, plastic or wood:

Firstly, the drill bits used are quite different. Average wood/metal bits cut into the material and draw it out. Using a bit like that only creates a large amount of heat, which gets you nowhere and severely weakens the bit and the glass (believe me, I’ve tried). A bit specifically for drilling glass uses a grinding method to remove material. A glass bit is not shaped like a normal bit, but more like a solid cylinder with a rounded head (they should have a blunt nose). Any good glass-drilling bit should be diamond tipped. In a pinch masonry bits can be used.

Secondly, grinding glass generates a large amount of heat (even if you’re using the right bit). The area you are drilling should be kept constantly lubricated. The easiest lubrication method is to use water, in a spray bottle, turkey baster, etc. At a bare minimum, the combination of the water and glass dust will create a thick paste. Thinner is better.

As for the actual drilling (grinding), go slowly, and apply only light pressure. It takes time, but you come out with a cleaner, stronger piece. If possible, drill halfway through one side, then finish by grinding the other half from the other side.

Since little bits of glass are going to be flying everywhere, you should DEFINITELY wear eye protection of some sort. It probably wouldn’t be a bad idea to wear a mask, either. Good luck, and I hope this was helpful.