This is a great simple video, which will show you how to properly use a glass cutter and runner. The very first step is how to hold the glass cutter, you want to hold it at a 45 degree angle straight on the glass. Make sure to try your best to avoid leaning it to the left or right and at a 90 degree angle, and also make sure to start off the glass before cutting. Depending on your preference you can either push or pull the cutter, it doesn't matter which way. Once you make the cut, take the runner and apply pressure to the glass at the cut mark, it doesn't need to be high up on the glass or to low and it should pop right off. If you ever make a mistake do not try and re cut the same line you won't find it, but rather flip the glass over and start again.