They protect both you and the student. Devise some kind of method for keeping track of assignments and attendance, and put a legend at the front of the gradebook. Gradebooks make it easier to handle grade disputes. For example, if a student goes to your supervisor claiming her D grade was the result of your dislike for her, all your supervisor has to do is look at the gradebook. More often than not, the student making such a claim generally has missed many days of class and many assignments.
Many departments provide photocopy or ditto machines for TAs' use.
Check with your department. Most TAs do not have phones in their offices. Check with your department. E-mail is a great way for students to contact you and you them. Technically, one hour per week for each 3 hours taught, but most teachers spend more.