As a year 7 form tutor, and a teacher of English, I'd say my approach is as follows:
Make expectations very clear.
In class. For example, you're expected to bring x, y, z.
Make sure you are on time to class. If you arrive after the bell, you'll be marked as late.
Uniform and appearance should be correct and smart. Etc. I also make sure each student has a copy of their timetable for class, and where they need to be for registration, assemblies etc.
There's a number of activities we do as a form on the first few days such as a school tour, familiarising themselves with their timetable, explaining when breaks are, when toilets can be accessed etc.
I don't emphasise detentions other than to say if they find themselves less than expected, detentions are there as a way to ensure they don't forget in a hurry.
I push positive rewards (points for being polite, kind, effort, attitude etc).
Any year 7 students I teach for the first time, I also allow them to be a few mins late for the first class as I know what it's like to be quite small and have to fight my way through corridors to a room I've never been to before.
I also give students in my form a piece of paper and ask them to write any comments or questions they may have but are too afraid to ask out loud. I say if they don't have a question, to just leave a nice comment or something they've enjoyed about their day. They then pop the paper in a bag I pass round and then no one feels embarrassed about any questions I read out.
I did, however, have a year 7 student removed from the classroom followed by a 15 minute detention on day 3, as they refused to open their book, write down the date, talked back, refused to stop talking, and was generally being disrespectful throughout the first 10 mins of my lesson. I had to repeatedly stop and speak to them. I gave them three opportunities to make better decisions but they persisted. 🤷🏼♂️
No amount of threatening detentions would have prevented that behaviour, it just would have scared the more sensitive kids.