Your current course
If you are in a professor's class now, you can easily talk about it. What do you like about it? What do you think is really interesting and attractive? What do other students like about it? What happened in class recently? You want more information. Do you think it is helpful or just funny?
Courses to attend.
If your professor is going to teach a course that interests you next semester or next year, you can talk easily. You can ask about the amount of reading, what topics are included, what the professor expects from the course and students, and even what the syllabus will be like.
You like classes very much.
There is nothing wrong with talking to the professor about the lessons you have had with him or her before. You really like it. You can talk about what you find particularly interesting and ask your professor if he can suggest you take other courses or supplement your reading materials, so that you can further pursue your interests.
Graduate school selection
If you want to go to graduate school, even a little, your professor is a good resource for you. They can talk to you about different study projects, what you are interested in, which graduate schools are suitable for your interests, and even what the life of graduate students is like.
The concept of employment
Maybe you like botany very much, but you don't know what you can do with a degree in botany after graduation. A professor can be a good person to talk about your choices (except, of course, a job center). In addition, they may also know some internship opportunities, job opportunities or professional relationships, which can help you.
Any course you like.
If you have recently reviewed a topic or theory that you like very much in class, mention it to your professor! There is no doubt that this is good for him (her), and you can find more topics that you don't know you will like.
The difficulties you encounter in class.
Your professor is a good resource, if not the best, for you to find or get more information about the problem you are trying to solve. Besides, one-on-one conversation with your professor can give you an opportunity to convey an idea and ask questions, which is impossible in a lecture hall.
Academic difficulties
If you are facing a bigger academic problem, don't be afraid to mention it to your favorite professor. He or she may have some ideas to help you, may help you contact resources on campus (such as tutors or academic support centers), or may just give you an inspiring speech to help you refocus and recharge.
Personal problems that affect study.
Although professors are not counselors, it is still important to let them know about any personal problems that may affect your study. For example, if someone in your family is seriously ill, or you are in financial trouble because of unexpected changes in your financial situation, your professor may help you. Besides, it is wise to tell your professor when these situations first appear, not when they become problems.