Never discuss a grade when you are angry. A test may have seemed to you to have been unfair, but don't label it as such when you're discussing it with the professor. Be specific but courteous when making you points. Remember, regardless of how skillful you arguments are, the odds are that your grade won't be changed on that particular test. But, if you make your points well, the next test may be much better constructed and may seem to you to be a fairer measure of your knowledge of the material.
Most professors are experts in their fields.
Many of them are not experts in psychometrics or applied learning. Realizing that very few of them have had formal teach may help you to understand their occasional shortcomings in these areas. Most good professors have gotten that way by trial and error. Improved teaching often depends on the kind of feedback they receive from students. Avoid being negative in your comments.