How do I cut 1/4″ thick glass?

I have cut glass for stained glass windows and regular double strength glass, but a friend wants me to trim some corners off a piece of 1/4″ thick glass. The last time I cut 1/4″ inch glass I remember it being Very hard to break along the score line. Does anyone have a suggestion about the easiest way to cut the glass, or how to get it to break along the score line without so much effort?