Get them to take a photo of their timetable.
They can get clothes ready the night before.
My DC gets everything ready the night before. School books are either in their school bag, or in a plastic box in their room. This is a cast iron rule. Any book not in either location has been collected in by the teacher. At the start of Year 7, I would assist to check exercise books, planner etc were packed, now this is done without my input.
There is a copy of the timetable on the fridge, for double-checking purposes.
I blu-tack a little note to the inside of the back door (which we use to leave in the morning) on relevant days. The note says 'Have you got your PE kit?' It's necessary because my child is the sort of dreamboat that will step over a carefully placed PE kit instead of think, 'Oh, look! My PE kit! Mustn't forget that!'
I step back with homework. That's DC's responsibility, although I do give a gentle nudge on the mornings when I know particular homework is due, as my child has a habit of completing homework then leaving it on the desk instead of putting it in their schoolbag to hand in.
If the school has a cashless, card payment system, make sure your child knows what to do or where to go when they lose their card. Likewise locker keys. My child has a (discreetly named) zip up purse for these things, including bus pass, which is kept in a particular blazer pocket.
I think it's useful to remember that whilst it is your child's responsibility to be organised, it is a lot for some kids to manage to start with. I don't think there's anything wrong with providing lots of organisational support to start with, especially if your child finds remembering things really hard. I teach, and it's awful to see how upset these new starters get when they forget things or make a mistake in the first few weeks. Anything parents can do to mitigate that is good, I reckon. There's a lot of stress for Year 7 (big new school, new students, grieving the safety of primary etc), without adding in a nervous breakdown because they've lost their bus pass. Poor little tykes!