Manage time by planning out the days and weeks. Schedule everything around the courses, to allow study time. Create a timetable, so schoolwork does not interfere with employment and social time. Keep a "to do" list of assignments to prevent lateness, which could affect the final grade. Prepare for distractions and interruptions along the way, as assignments change.
Prepare for class by completing all reading assignments, and finishing all projects and papers for each class. Participate in class discussions, and speak to the class about the material being covered. Take advantage of the bibliography provided by the professor and do follow up reading. Ask good questions and don't be afraid to ask for clarification; sometimes others in the class have some of the same concerns.
Take good notes in class and write down instructions, numbers, specific dates and times. Write notes in the margins of books and on papers. Use highlighters and different colored pens to differentiate information. Listen intently, and try to not write down everything the lecturer says. Spending too much time writing, means you aren't listening. Graduate school professors are experts in their field and sometimes can be difficult to understand, or don't know how to convey information easily.
Ask for help. Approach the professor after class, or in their office. Many graduate professors earned a doctoral degree in their field, and want to share their research, and what they know. Students who want to learn, will earn the respect of professors who want to teach.