Students remember a first day that gave them something and forget one that only listed rules. So plan an actual class. Include a genuine welcome, a small taste of the subject that reminds everyone why it is interesting, the essentials of how the course works, and a short activity that gets students doing something rather than only listening.

You do not have to cover everything on day one. It is better to do a few things well: make people feel welcome, spark curiosity about the material, and set clear expectations. A first day designed with care signals that the whole course will be worth their time, which is exactly the impression you want to leave.