Simple things like:
Asking before taking
Understanding that when a grown up says NO, then having a parent say yes when they heard the no is just rude.
If something gets broken, fess up to it. (it is not about punishment or replacement, it is a responsibility thing and kids need to learn it)
Not teaching children that every party, event, etc is an all you can eat buffet regardless of whether other people have eaten.
...and lastly, I do not give YOU free parenting advice..... (I might be judging you at the moment, but i keep my mouth shut!)
I feel bad thinking these things.