There are three categories, in my opinion, of pick up lines for girls – those that work, those that do not work, and those that work only for certain types of people.
Here Is An Example Of Two Pick Up Lines (My Favorite Ones) That Work:
1. “Hey”. Say it with a smile, don’t forget to come right at her face, and have a good, friendly vibe that just pulls people in. Ideally, you also need a very challenging voice to come across like a gorilla, so to speak – just remember to smile and have that disarming vibe at the same time.
2. “I like you” or “You are cute”. Same principles should apply to this pick up line, and the same prerequisites need to be adhered to to make it work. Basically, just be confident, or at least appear to be confident, smile and approach that girl and tell her with full honesty and with no ego (as in, with no ego shield that tries to tell you “well, I will smack talk her if she rejects me!” – no big deal. Be disarming.).
Here Are Some Of The Pick Up Lines That You Could See On TV – My Favorite Ones Are From Will Smith
http://www.youtube.com/watch?v=NH4BJ9B1lrw
Remember, though, I personally think that all these pick up lines for girls are a little bit cheesy, and it will be very hard to pull them off without coming off as a try-hard (and guess what? Being a try-hard is the last thing you want to be if you want a girl to really like you).
Anyway, these are funny. I don’t recommend using them, though. Although if you can pull of this Will Smith manner of speech – then ok. Usually, though, they can get you either a laugh or an awkward moment. After that, you still need to make a conversation going.
3. “Girl, you look so good I wish I could plant you and GROW A WHOLE FIELD OF YO”.
4. “I think I’ve seen some pictures of you before… Oh yeah, it was in a dictionary next to KABLAAM”
5. “yo baby your feet must be tired because you’ve running through my mind all day! COME HERE!”
Another character who throws out very good pick up lines for girls is Johnny Bravo
Very weird style. Amusing, if you are into it.
However, if you really want something that works, you should either test it yourself on the girls, or you should just copy the phrases from those who know what they are doing. You won’t believe this, but shocking lines like these:
6. “I want to put a baby in your tummy”
7. “I like salad”
Work.
The Main Lesson That You Get From This, However, Should Be
You can say whatever you please (almost) as long as you say it right. And even if you screw up, you should just continue talking as if nothing happened – the majority of girls find that the personality of guys is what makes the difference, not looks or fancy lines.
I mean, a line is like only a few seconds long. It is not like she will drop her pants after just a few seconds. Usually doesn’t happen that way, at least, so you’d better have something else going on. 
Oh, and again, you can say whatever you please to as long as it is congruent to your personality.
One guy was successfully picking up chicks in Barcelona by shoving hips into girls and pretending like he was a tiger or something. Weird, right? Well, that’s why girls are emotional.