The best way to pay for printing is to insert your money directly into the tower at the print station. Do not use your student ID. Just insert your money and follow the prompts on the screen. You can put in up to a 5-dollar bill and get change after you select your print job.
If you want, you can put money on your Student ID card and use that to pay. Do this if you want to make copies or print outside of the LRC, or if you only have larger bills and can't get change. However, cards sometimes get bent and cause problems in the machines, so unless you've got a good reason, it's better to pay directly and leave your card out of it.