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:
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.