First of all, I think you mean QA for Quality Assurance.
You start your test planning with a thorough understanding of all the requirements of the projects - requirements are the "what" of the project. What kinds of printing jobs will need to be done? What applications will print to the printer? What kinds and sizes of paper? What OSs do you have to support with printer drivers?
Define all the whats - and then you have to create test cases which test all the whats. To help focus, think about the risk factors as well - the highest risk items need to be tested the most.
There are web based sources for test plans and test cases. I recommend www.rexblackconsulting.com. I've taken a testing course from Rex - he has written some well received books on the subject. There are other sources too - check google.
There are literally hundreds of books on the subject - I recommend you read Rex's book, or Systematic Software Testing(www.sqe.com)
James