I think the first piece of advise thats comes to mind, would have to be about the practical aspects, which is: If you just spend that extra 5 minutes cleaning or filling a piece of work at the beginning, it will save you a lot of time and effort at the end when you finally come to cleaning, file and polish a piece of work...basically saving you time in the long run.
Another great piece of advise that some makers lose sight of is: You should always make for yourself, even if the piece is for a specific brief, make sure that you are happy to put your name to it and make it so its still in your style.
Well for number 3, i think it has to be one from the mother. My mum always told me that when you do something, do it to your best ability! Even if its never going to be as good as someone else, at least you knew that you did everything you could, to do your best.