At a club last night I was running an experiment on giving yourself ludicrous amounts of confidence. It worked like crazy so I'm inflicting it on ya'll.
This all comes down to having a solid frame and deciding what to focus on so if you aren't able to take control of your thoughts even a little bit, this won't work. Get some experience meditating first.
Here's the frame you need to keep: "Everything in the universe exists for my pleasure, whims, and amusement".
How to do it: Imagine it's true. Just pretend until you can internalize it.
If you hear a sad song, imagine it's sad because the songwriter only wishes to be graced by your presence but has never been able to meet you. If there is a happy up-beat song, imagine it was written solely as a homage to how awesome you are.
When you see people dancing, take pride in the fact that they are dancing to your song and are overcome with happiness that you exist. Obviously approaching someone is the greatest gift she could ever receive but even if she reacts negatively it's probably just because she's overwhelmed and intimidated. Poor thing.
Remember that many many people laboured for endless hours to construct the building you are now standing in, just so you could have a smooth floor under your feet and a roof to keep the weather off. Same goes for anything; clothes, drinks, food, etc.
Ya ya, it's easy to logically attack this idea, but you would only be hurting yourself so just play along.
Why this works: You can only think about a limited number of things at a time. If you have low confidence then you probably spend a lot of time thinking about what other people think of you. "Does she like me? What if she has a boyfriend? What if her friends cockblock? Am I too ugly?"
So by playing an imagination game you limit the amount of negative thinking you can do. You are keeping your brain busy. Imagine you are the king of the world like this and the negative thinking will be less intense.