You can start off by imagining yourself being confident when meeting new people; practice seeing yourself in your mind's eye confidently smiling and shaking hands, and having a pleasant conversation.

When actually meeting the new person, don't necessarily think in advance what you are going to say in your conversation; just say it, speak your mind and go with the flow - as long as you are not willfully hurting the other person. And make it a habit to speak loudly and clearly.

And lastly, always look your best and develop a good body language - stand erect, walk well and look in the eye during conversation. If this seems difficult or unnatural initially, do it anyway, and keep doing it until it becomes natural. In other words, as it is typically said, just fake it till you make it.

Try to take your mind off the fact that its a "game"; see if you can "imagine" that its a practice session. In other words, it shouldn't matter to you if the ball is hit correctly or not; or if you win or lose the game. Just hit it like you usually do, and try not to focus on what the end result could be.

It may take a bit of practice, but eventually playing like that would become second nature, and your shots in a game will automatically improve.

Constantly question and second-guess their words and actions, and seek other's approval for them; be unnecessarily critical of others; mumble or speak incoherently; and/or show the classic body language signs of low self esteem - like no eye contact or hang their head down during conversations, or droop while walking.

One of the first things to do is to quit criticizing yourself. Watch for self-criticism - the moment you recognize it happening, pull yourself up short and stop it.

Being short need not necessarily be a liability; if you carry yourself well with confidence, it's all that matters.