Positive attitude

One of the biggest behaviors that wins people is just being positive, compliant, agreable with people. It doesn't mean that you're acting to be nice or pretenging to be happy. You're communicating positive attitude, telling the person that everything is alright. The other person might be angry, negative, argumentative, but you're positive. It's not that the other persons behavior is not negative, it is, but you do not signal that untill you want them to change and you have a specific thing that is easy that you have them do which has positive association to it for easy influence.

Being positive doesn't mean being fake or pretending doing anything you don't feel like doing. It is merely a form of communication which says everything is alright, there is nothing wrong, I'm happy. You might not be happy, there is any number of things you might be feeling, but for the purpose of the communication, you are sending out a relevant message which tells the person what to do. By being happy, agreeable, cheerful, you're telling the person to carry on.