And some pizza, oh, beer too, You need that, or any glass bottle really.
Step 1: Supplies
Also, You will need some food too, pizza is the best choice, goes good with making things.
You might want to put in a good movie or some awesome music as well.
Step 2: Start filing.
Wear a mask too, will protect you from inhaling all those dangerous glass dust bits. :0D
Eye wear would be nice as well, No one wants glass in the eye.
Start off just filing away a bit at a time, gradually turning the bottle as you do so, keep going over the marks you are making, occasionally tap it on the edge of a hard surface, carefully so you don't shatter the glass, Keep this up for about 15 minutes or so, depending upon how much effort you are putting forth and it should just pop off the bottle.