Instructors expect students to attend class regularly. Instructors expect to begin class on time. Students who arrive late are distracting to the instructor and to other students. Instructors expect students to submit assignment on time and according to instructions. Instructors expect students to let them know if they are having problems understanding or working with the material.
Many instructors are anxious to help students who ask for it.
See the instructor during the office hours noted on the syllabus if you need help. While most instructors want students to participate and ask questions, most do not want one student to take up large segments of class time. Some instructors prefer students to hold their questions until the end of the lecture. Try to learn what each teacher expects during the first few days of class. Different instructors expect different things from students and teach differently.