Make sure your lips aren't chapped. make sure your breath is good. Nothing turns a woman off faster than stinky breath and chapped lips. [EDIT: A nice soft sweater is a bonus, if she puts her hand on your chest during the kiss.]
Stand close, or move in to within reach. Eye contact... calm, confident, but with obvious desire.
Gently reach out to the side of her cheek, letting your fingertips VERY slowly graze her cheek as you slide them under her ear, brushing her hair towards the nape of her neck. Watch your fingertips as they move into position, then look at her lips. Sometimes I even cock my head slightly so she sees me focusing on my contact with her.
Move in very slowly, so she has a chance to process the sensations. If she's not interested, she'll move away or stop you... respect her signals. Close eyes on the approach, when she does.
Contact should be soft and gentle with closed relaxed lips for a couple of heartbeats, then a light tension pucker on the upper lip. Only move back a little bit, and linger within a couple of inches of her. Re-open eyes, and watch her reaction.
Of course, this is only one scenario, but it's a reasonable starting point. Don't get tongue involved too soon (or at all right away... that's pretty personal). Take your cues from her behavior.