Make the first day of classes interesting to your pupils. Introduce yourself and let the pupils introduce themselves too. It depends on what subject you are covering, if the curriculum is departmentalized like english science, music & arts or social studies state the name of the book to be use and what materials do they need for the subject, how many times will they have periodic tests or tell them about quizzes and weekly test.
For me the first day of meeting them is very important so you as a new teacher should make a lasting impression that learning is a one to one process that each pupil is given every chance to excel so tell them to approach you whenever they need something or they are free to ask questions and that you are there to help . In this way there will be an open communication during class discussions.