Hey mate.
Ok, me and my mates are considered the "cool" guys in our year, and let me tell you, that alot of the guys that i originally thought were "unpopular" became good friends with our group.
Everyone, not just women but guys also, like someone confident. You are either their close, confident mate, or the aquantaince that they like to pick on and play jokes with.
Choose which you would rather be.
Be confident, big rule.
How to know to say? Talk about anything, don't bring the mundane and usual "What are you into?" jack. Nope, talk about anything that you find interesting (with the exception of video games) and that you think may interest her. Be casual, don't cling onto the conversation like you need it to work out or you will die. If you don't speak to her on a regular basis already, maybe just drop a few lines of tease here and there. Eventually, she'll be comfortable speaking to someone even if they aren't considered "cool", cause they are funny as hell.
Here is an example of me speaking to two hot girls 3 years older than me yesterday at the beach:
Me: Yeah, those are my mates, i love em.... (pause) don't ahh, tell them that.
HBs: Aww thats so cute, yeah me and Daniella are in love, we can like look at each other and know what each other is thinking.
Me: Wow, nice, whats she thinking? "Man this guy is hot, i wanna get into his pants" Right? Yeah thought so. Women are perverted!
HBs: Haha! Noooo!/ I'm not allowed to say what she is thinking(wink)
Me: I think i have a mate who im like that with, his name is Jake, he is swimming just over there. He also plays the guitar, one of the reasons why we are so close. We would see something interesting, and just look at each other, we know what we are thinking...
"Man i gotta get that Ukulele!"
HBs: Giggle, laugh.
HBs: Oh you play the guitar?? Nice! (Notice natural topic change)
Me: Yeah, i love my music, i hate the crap on the charts at the moment, i mean, if songs like "Crazy Frog" can get into the music industry, it tells you our society is well and truely screwed.
HBs: *Giggle* Laugh* Positive reactions.
Me: Do you guys play an instrument?
HBs: Nah
Daniella: Oh well, i write music...well like lyrics
Me: Really? Awesome, I'll play you a song and you can sing ok?
Daniella: Noooo! Wait, no!
Me: Oh, shy huh? Pftt, you guys are boring!
HBs: No! We are fun!
Me: I usually like people that are you know, adventureous and spontaneous.
HBs: We are! / We're adventureous!
Me: Prove it... whats the most craziest thing you have ever done?
Etc etc etc...
See? It just comes naturally, and its interesting, i throw in some C&F and bam, way past social hook point.
How to improve conversational skills? Easy.
Talk.
Talk alot.
Thats it, go out speak to everyone, learn to talk about interesting things, as well as small talk or fluff talk. Watch dramas and soapies like the OC and notice what they speak about.
Speak to your parents, your friends, your teachers, everyone more.
How do you know you are improving?
When you can speak to a hot girl, and notice she is actually interested and engaging in your conversation.