Need help with serial ports

I'm new to programming and I am wondering the best way to use the serial port to recieve inputs from 3 simple circuits. All I have to do is to know which circuits have been completed and in what order they where completed in. This is for a knowledge bowl type of situation with three teams. Also can we recieve the inputs through the different pins of the serial port or do I have to make some hardware that gives each strip a different binary number. Any help would be much appreciated. thank you in advance.