You need to wait for some indicators of interest before asking a girl out. You can't just walk in there and ask strangers out or else you'll get shot down too often. Some guys will tell you that this is a "numbers game" but I for one prefer having the numbers stacked in my favor. Now, here is the fun part, if she does not show some interest, then you can always force the interest through your mastery of the game.
I could write volumes on this, but I'll give you the basics for now, since you are still a beginner.
examples:
1. You ask a girl what her name is.
She replies and doesn't ask you what your name is.
This usually will mean she is not that interested.
You can force the interest with "hey, I know you're dying to know my name, but you're too shy to ask, so it's Stavrogin" and you smile.
If this gets her going, then she's interested, if not, you need to try something else. If it is unwinnable, then you move on. But in my view, you're better off practising this stuff, so keep going.
2. You ask her "what do you do for a living?"
She says "I'm a student, what do you do". She's interested. You need to rehearse a clever answer to this. You can't just say "I work at McDonalds". You need an original spin on what you do that will hook her.
If she doesn't ask what you do, then she's not that interested. In which case, you can force the IOI by saying "You're probably not asking me what I do because you've seen my work on tv".
She'll say "what?" and you'll say "You must have seen the movie Pearl Harbour where Ben Affleck is leaning over the railing of the ship and they show his naked butt. We'll that was me. I'm a model". Say that with a smile too. If she laughs, then you're in, and you switch to telling her what you really do in an interesting way.
In conclusion, you should definately always approach and be fearless when asking out chicks. But also make sure that you've done all you can by getting her interested enough to want to spend more time with you. That is the whole point of asking out. The chick has to want to spend more time with you, and if you display confidence, humour, ****iness, etc in the first few stages, she'll have better chances of wanting to see more of you. From there, you need to go into deeper "rapport" stuff, when you or on the date, or else you'll just be a clown, but that is the subject of another post.
Cesare Cardinali