There are so many things to write, but there are some wonderful answers here – I would just like to contribute these four thoughts . Everyone needs parenting from time to time – so  gifts of successful parenting don’t have to be limited to your children – your friends, acquaintances, work mates, the person sitting alone looking distressed, someone else in the queue, us – we all need successful parenting no matter how old we are.
1) You never know your children – when you think you know them, you have them fixed as an idea in your head. Then when they stop being like the idea in your head that can feel like a crisis, and you may find yourself trying to persuade them to be the person you believe they are – the one they “should” be. Discover them every day – find out who they are TODAY. Let them change their minds, their behaviours, their sense of self…life is a huge experiment in becoming someone that feels right…and there have to be some big detours to find out what matters most.  I have three complete individuals on my hands and they keep amazing me with their discoveries about themselves. Be willing to be amazed and impressed by them and their discoveries, and tell them so – that makes their discoveries real to them, and that way they can build on what works about them. Your child will become someone you couldn’t possibly imagine – so thinking you can define them, or believe  “I know you better than you know yourself” is an illusion. Allow them to emerge.
Criticism is virtually useless – it tells them who they are not – you cannot build on someone you are not.
2) Present ALL the  choices right from as early as you can. Include the full range. Allow them to imagine their own way forward through the scenarios of choice. By telling them that, “You could swear at your teachers and call them names – that would tell them wouldn’t it?” they get to entertain the option, to explore it. I thanked my kids for going to school every day it hurt them to do so – “Thank you for keeping me out of prison”. They knew that the choice to stop going would be attached to serious consequences for me and their mother, as well as for them, because they knew they had the choice. We explored everything this way – sex, recreational drugs and alcohol. They know they could try them all if they so wished, without us knowing if need be, just as many of their friends have and do. But they have all three chosen that they do not want to try them. My adult son is tee total by choice, my older daughter has a glass of wine once in a while and my younger teenager is fascinated by the range of options and clear that she will try what she feels like when her brain is fully developed, as an adult “at some point”. By stifling or censoring choices, by disapproving of them, it leaves them unexplored, and this promotes their allure. Exploring ALL the choices, even the anti-social and illegal ones, promotes a magnificent way to develop imagination – and I have seen things we have explored appear in their creative writing and plots in their stories as well as in the advice they give their friends.
3)   Be who you are – let them see your flaws, your feelings, and do not present yourself as a super-human, whilst doing what you are ashamed of out of sight. This is lying. Let them see how you clean up your messes, put your wrongs right and how you say “I’m truly sorry”. I am convinced that “I am truly sorry” matters as much as the words “I love you”. I see the results of people being forced to pretend that they are super-human, over achieving, parrots to their parent’s pretences. We are all human. If you are taught to pretend that you are superhuman by a parent who pretends to be super-human, ever-cheerful, always positive, a mistake free zone, always generous at their own expense, never asking for help or support, then you are condemned  to failure. Failure leads to shame, and shame is the platform upon which depression thrives. Be human – clean up – and let them see your mistakes. They can see through your pretence anyway – they are very perceptive.
4) Admit that you are making it up as you go along, just like everyone else is.  Everyone is making it up, making themselves up, making everything up as they go along. Life and the selves we are becoming are a wonderful creative adventure – as long as you are willing to make it up it continues to be full of surprises. Your kids are making themselves up as they go along – watch and be amazed. Just point out that they are not alone in this – everyone is doing it.