Even if you haven't had a date for ages, you have to act like it doesn't matter much to you if she's interested or not. Even if you really like her, you have to give her the chance to back out gracefully. It's funny, but if she knows that, she will be far more likely to want to continue talking to you.
There's a story about a centipede who started to think about which leg to put forward first, and he got so confused and worried, he fell over. That's what happens to you if you think too much. You start to think about all the things that could go wrong, so you give up before you start. So don't think too much. Just go up to her and start talking. Don't get nervous, and don't think about what to say, just say the first thing you can think of.
The fact is, you're a very special person, aren't you? So you don't need to try to "put on a show". If you just be yourself, your specialness will shine through. Women are most impressed by guys who "act real". They really don't like men who try to act as though they're someone else.