I've read a lot of, very useful, threads with advice about the baby/ toddler years but not many (if any) for when they are older.
I'll start.... if there is any chance your child(ren) are likely to go to university, start saving as soon as possible and watch Martin lewis's videos about student loans and fees. So, so many people don't seem to realise that the loans no where near cover how much your DC will need to live on and parents are expected to make up the difference. Yes, more DC are expected to get a job, but it's still not likely to make up the shortfall.