http://www.wikihow.com/Be-Coolread this article meaning of cool. I copy paste some steps.
these steps are not only for child but for adult to adult too
Remember that people are your equals. Even a group of people is equal to you. If you're talking to a potential employer, a group of wealthy donors, a child, a stranger, the president of the United States, or an attractive guy or girl, for example, remember they are neither better than you or worse than you are. They should be treated as you should be treated. Be respectful of other people, but expect that they will accept you as such.
Don't be needy. Remember cool people are not needy or desperate, unwaveringly. Instead try to solve problems yourself. If you are not needy people will want to help you or will ask for your help. This quality attracts people. Neediness is a big turn off dont do it or end of story.
Present yourself in a positive way. Smile. Be a habitual, unrepentant over-smiler, with every grin being a genuine one. If you smile when you meet someone, you instantly appear confident, friendly and relaxed. Confident, friendly, relaxed people are much more appealing than their uptight com-padres.
Be friendly, but not excessively eager. Everyone loves someone who is outgoing, but nobody likes someone who is overly excited. Many people find someone who is overeager to be annoying. Try not to force yourself on people. Smile and strike up a conversation, but make sure you know the line between friendly and obsessive
Use humor. Cool people always use humor and ease in any situation. They don't get annoyed and angry, and no matter how many bad things happen to them they don't take it too harshly; they make jokes about it. They have excellent emotional awareness and they don't let bad emotion affect them, they have awesome emotional control and understanding.
Never argue. When you're cool, arguing is always canceled. You realize winning an argument is pointless. When you know you're right you just know it. You don't need to waste time, effort and energy by attempting to persuade someone who hasn't seen the things you have seen.
Edited by amarjeet73 - 01 December 2012 at 4:44pm