Easy to cut glass. I have cut thousands of pieces since I do stained glass work. Get a GOOD quality cutter at the hardware store, like a Fletcher. Wipe the glass with a little fine oil where you are going to cut. Oil the end of your cutter, where the wheel is. Mark where you want the cut with like a felt tip. Use a square and line up the cutter wheel with your mark. Press down firmly, but not HARD amd pull in ONE motion. Do not go over the same spot twice, unless it did not score the glass. At the edge of the glass place your index fingers on the bottom on either side of the score line and your thumbs on top on either side and apply pressure. It will snap. Like Dick said practice on some regular glass fist. A couple of cuts and you will get it.
Next class, cutting circles for clock face pumps....
