There are tons of breaking & cutting tools out there. The most primitive tools would have to be the hammer and a towel. You essentially place the glass in the towel and repetitively smash the glass. I find it the quickest way to break organic looking pieces yet also the most wasteful. You'll find yourself hitting certain areas often to break larger pieces but at the same time almost powdering the smaller ones. Some people recycle that dust as a "Frit" a grain sized glass used for fusing.
The next step up would be a glass cutter and oil. These glass cutters can be found at your glass dealer, stained glass websites and at hardware stores. All will definitely carry a simple cutter. Which looks like a small pencil with a metal ball on one end and the other has a carbide wheel. These cutters are worth it to the cost conscious person but not if you really want to get into the art of stained glass. They are called disposable for a reason. Eventually the axle supports for the carbide wheel was ware from use and the wheels edge will dull. There are definitely highers quality cutters but with quality in the glass world, cost reflects. For someone who plans on making this a permanent hobby or career, you're not spending too much - you're making an investment. I have a solid brass cutter that is self lubricated because you fill the cutter with glass cutting oil.
Now lets talk about oil. In order to cut the glass, you must be using oil to lubricate your cutter other wise - you will not score the glass and make it weak enough to make with your hands. There are oils formulated for glass cutting, but you can used tiki torch oil, canola oil, any oil actually. Though you can not fill the disposable one, you must use oil with it too. You can fill the cap of your oil and place a small sponge square in it so that you can quench the wheel without over or under saturating. There are other tools like circular/oval and straight edge cutters which are also up there in price. But are very useful and require the quenching technique.