trial and error and reading the protocol documents. Serial is a dying interface as far as tech goes so I dont think you'll find a class at school for it. It's pretty simple really, There are 2 aspects of it that you need to know, the hardware side(pinouts of your connectors) and the software side which is the protocol. This info is in the protocol document of whatever equipment you are trying to control. If you read it and play with it then it will begin to make sense. Try hyperterminal on your pc to quickly check your strings.