Meeting with Professor for letter of recommendation
You can expect questions about your plans, your interests, strengths you want the letter writer to focus on, any weaknesses in your application you may want to assuage, etc.

In other words, this sort of meeting is designed to allow the recommender to write you a better letter. This is a very good approach by the recommender - a professor who knew you more closely might not need such a meeting, but all this professor has to go by is your participation in his course, which may not be all that memorable. He may come across as "rude and angry" but in this context it seems he has your best interests in mind, so you should be very thankful. An alternative would be to write a curt, impersonal recommendation ("Of all the students I had in my Important Studies 301 course, my records show Luqman Saleem was one of them.") that will do you little good. 

It may be helpful to bring along your CV as well for the professor to keep, if he has not asked for one already. Be ready to answer questions about why you want a PhD, your research interests, etc, and have a good reason for why you bothered to ask this particular professor - what skills or abilities are they best positioned to write about that will be important for the programs you are applying to?