Cold approach:
“Oh, hey, you’re a little late... But if we hurry we can still make our 1pm lunch table.”
"When was the last time I took you home..?" (more advanced, but work up to it)
“Hey… you know what… I just couldn’t continue my day unless I met you”
“Wanna Go Steady?”
“I know your out of my league, but I had to tell you that your smile is adorable… (self effacement allows you to open with a compliment. however, don't usually open with a compliment without putting yourself down a bit - but you can do it in a bit of an exaggerated way, like your intentionally being humble, which you are. It still gives off confidence, and shows some skill with the ladies, and shows that you know enough to know that a pure compliment is a bit cheezy on its own, even if both her and you know that your a confident conceited bastard in real life.)
(I came up with this one night) Pick out something that sh'es wearing, doing, etc.. if its a little funny, then:
“So, when am I going to get to show my new #@@
[email protected]# loving/wearing/etc GF around town?
you can keep going with this if you want:
Her: never
Me: That might cut into our 1 on 1 time.
Me: “Just one drink/date. If you don’t like it, we can just have some insane sex and go our separate ways”
Her acceptance anywhere along the way, and its on. but you gotta be having fun with this to get away with the last line. If your convincing and charming enough, it'll go over fine. Body language and confidence has to be there the whole way.
"Wanna go to the Prom?" Sounds cheezy, but girls love that prom shit. They're sentimental for the most part. Also, its so stupid, and they think its cute (well, most girls do that aren't complete jaded angry bitches), so it works. It makes them giggle. Thats all you need.
I have a lot more, but this is good to start. I pick one usually based on the girl and the place (bar vs anywhere else usually) Just remember, you don't care about whether she accepts your opener or not, your just there to have a good time. Stay upbeat, and don't flinch if she does or doesn't accept your advances. Don't expect a good answer, just have fun, she will then have fun, and your in. Just keep moving it forward and DON'T be her friend. I mean, talk and connect with her, but also be a sexual threat, always.
Remember, your first goal is to get her to take down her defenses. Usually that means making her laugh or smile with your opener, no matter how much she would naturally resist this urge otherwise. Thats why cheezy stuff like "Wanna go to the prom" works a lot.
Your second goal is to then take it a little sexual, even a little hint of sexuality will work, so that she sees you as a sexual being, and not just an a-sexual funny guy. The key to not being creepy with this is not waiting for, or otherwise showing you care about her response.