Arriving early on the first day of class and talking informally to students may help you relax. This message will alert any students who are in the wrong classroom to leave before you begin. Call the roll or ask students to sign in. Have a contingency plan if more students than you can accommodate want to enroll. Check with your department to see whether policies exist for preferential enrollment.
Some faculty give preference to graduating seniors.
Others make certain that students have the prerequisites and then select enrollment by lottery. Mention department course policies. Explain procedures for wait lists, adding and dropping courses, and so on. Know where to refer students who have problems in these areas. Explain the procedures for the course's sections.