Some parents are not aware that they are THE role-models for their child. This already starts in the early stages. Yes the little ones who maybe even can't talk will observe you and copy your behaviour.
Sometimes this can be funny and oops... that wasn't what I wanted them to pick up on. So be aware and think before you react, for example:
in anger when driving behind someone who can't drive.
when the lady behind the counter isn't as nice as we had hoped to be and we are already wound up a bit... stay calm and express your own irritation calmly but firm.
when you have a wine or a beer and you still need to drive and be safe.
when you smoke and don't want your kids to smoke.
And I know this isn't easy, certainly not when we are agitated or annoyed about someone else. But keep in mind, kids are watching and take over your behaviour towards others. When you make a mistake admit this and tell them what you could have done differently.