You want a song that makes you feel really good inside, that makes you want to smile. It also needs to be something a bit bolshy, so that it gives you a "Go Me!" feeling too.
For some people it will be an angry feminist song, for others it will be a Disney style pretty song, for some it will be totally unrelated to the words and just be something that brings up a feel good memory, but for most it will be something in the middle, a girl empowering song.
Mine is Supermodel by Jill Soble. It was so fab in the movie Clueless, check it out below. Mind you some of the words shouldn't be taken too literally, e.g. I didn't eat yesterday, I'm not going to eat today and I'm not going to eat tomorrow! That totally isn't me, I love to eat ;-) just eat healthy. But the lines: 'Cos I'm young, and I'm hip, and so beautiful! Those make me feel it.
You need to listen to your theme song several times before you go out, or when you need an extra boost, and it should really pump up your confidence.
Then at that crucial moment, like when that perfect boy approaches, you need to play it in your head, and then, just like that, you will feel all pumped up and confident again. Chances are that as you play it in your head, you will start to smile, you will look more confident and sexy just because you are thinking of your very own feel good theme song!
So get listening to everything that makes you feel empowered and choose one just for you!