If the previous director was well liked -- change as little as possible and pick your battles.
If they were not liked, you will have an easier time implementing change.
Don't change too much too fast regardless.
Learn the kids names as quickly as possible and establish a positive rapport with the kids
Make sure you and your assistant are on the same page.
Be prepared for resistance, especially from the upperclassmen. Know that they will eventually graduate and you can implement more change the next year.
Be clear with your expectations and communicate them frequently. Be consistent with it.
Make sure you have admin support on any major changes you want to implement. Community support as well depending on how involved they were with the previous director.
I'm sure there is a ton I'm missing, but that's a decent start I hope.