Kissing girls you don't know can be fun!
You'll know when the time comes...she'll get those dilated pupils, that stupid-ass grin, and she'll start talking in THAT voice (if you've ever been with a genuinely aroused female, you know what voice I mean
).
If you're going to go for a kiss, THAT is the time to display the utmost confidence. No hesitation, just take what you want. And even if she turns away, DO NOT be embarassed...pretend like you expected it to happen and it just means you have a little further to go (assuming you've gotten "buying signals" up till now).
If she turns a cheek or something, just give her a nuzzle...make face-to-face contact, it seems to help break down that anxiety that comes with the first kiss. If she literally recoils, you definitely moved too soon.
And yeah, girls generally don't kiss guys they've just met, unless they're horny as hell, so usually this means you can escalate the situation as necessary.
Just take your time and be gentle and firm at the same time.