How do I keep my daughter's room organized?

Bins and cubes with clear labels, then assign her a day each week to ensure it is cleaned and organized. If she doesn't complete the task, then you can revoke a privilege (no tv, no sleepover, etc)

There are many factors: age, personality, space, amount of items. The biggest in general organizer I have found is bookcases. You can add bins if needed. Double closet rods if possible and use thin, flocked hangers. I had a dry erase board in my daughter's room with her chore list and which were daily or weekly with day of the week. My biggest accomplishment was being able to shut the door and leave her with the clutter, as long as it was clean. It helped that her room was upstairs and easier to ignore. Good luck!

Keeping kids organized (and getting them to pick up their stuff) is hard. This post might help: https://jessicawellinginteriors.com/organize-kids-clothes-for-school/

Get rid of stuff to reduce clutter and introduce her to the Kon Mari method

You can try helping her clean up and organize together as a team, that way she can learn from you how best to keep things tidy.