First Periods...

Does anyone have advice on a girls first period? Like how to handle it as a parent? How do you know your kid is about to start? How do you handle their mood swings, cramps, and tools? For example, how young is too young for tampons and what is the best pain reliever(pills, liquid). I know these are lots of questions, but I am a parent and I'd appreciate any advice you all can give. Thanks!