It is usually a good idea to get your own work cleared away before the onslaught of midterms and papers. You might also wish to set a limit on the amount of time you will spend on each essay or exam. Find out from the professor running the course how many exams and assignments will be required during the semester and when. You may be able to assist in the preparation of the exams or essay questions, giving you a much clearer idea of what to look for when grading. You could even take the exam yourself to learn about tricky or ambiguous questions.
Some professors ask their TAs to assist in making up exam and essay questions.
When the papers come in, some professors will also meet with TAs to talk about the students' responses and to decide precisely what the grading standards will be. In all your TA work, you will be pressed for time. If you enter the profession of college teaching, you will certainly find that the problem only gets worse. Planning, organizing, and communicating are an investment of time and energy, but they will ensure that your courses run smoothly.