First Day Advice for a Newbie

I just accepted my first job and I’m looking for any tips and tricks/ do’s and don’t’s from you seasoned subs 🙏 It’s a half day so I can at least ease in with that but it’s also first grade. Not too worried about the age group since I’m well acquainted from having tons of little cousins I’ve looked after for most of my life BUT I am worried about how much I’ll be required to teach. I have a friend who works as an elementary Sped teacher a county over and they said they recently had to take over a class from a sub who couldn’t teach the material correctly. “With pacing kids can’t have any free days.” I know it’s different for each class and district but anything you all can give me would be much appreciated! Also what do you guys usually wear for the job? HR hiring manager just said no shorts or flip flops but idk if there’s a general rule (meaning an unspoken professional one) against nicer jeans.