2- Don't use pickup lines
Pickup lines smell bad and make women groan, not moan. Let the situation dictate your approach. To seem — and actually be — spontaneous, commenting on something she's wearing or has been doing can work.
For example, "I was just noticing how well your shoes show off your calves, and although I'm sure you're already aware of this, sometimes it's nice to get outside confirmation." If you choose to comment on something she's been doing, make it positive, such as "You guys sure seem to be having a good time," rather than, "I've noticed you've been twirling your ice with your swizzle stick for 15 minutes now." No stalker talk.
Anticipate her possible reactions and how you will follow up to put your mind at ease. You will get much faster at this with practice. And have some open-ended ("how" and "why") questions ready. Remember: Most people consider the best conversationalists the best listeners.