I worked in a secondary so covered most things before she started.
It is important that anything you want her to hear about from you gets told now, that's any topic where misinformation is dangerous or will cause upset. That's everything from Santa and the tooth fairy, sex and consent, to what porn is and why it shouldnt be watched, what's vapes are and their dangers etc. Have a very open relationship where she feels she can ask you anything.
Tell her to get involved in as many after school/lunch clubs as possible that way she'll know more people so that when classes switch around she'll always know someone even if they aren't best friends - it's really important in year 7.
Don't tattle tale minor things, yes if something is dangerous or harming you or someone else tell an adult but someone irritating you needs to be ignored, someone taking the last glue stick so you have to wait etc doesnot need to be told to a teacher.
Keep on top of WhatsApp, it's great and awful at the same time.
Set up a specific time of day to catch up with no devices or distractions for either of you, we do the first 30 mins when she walks in, I WFH so take a break and make us both a drink and cheese and crackers and sit and talk about her day, what she learnt - she'll try and teach me, drama with friends, any homework she has, she asks me about my day in return. It's a great habit and beneficial to both of us. I then leave her alone to do what she needs to do until dinner time.
Also a doing one, make your house teen friendly so she will invite her friends around and you can get to know them.