The thing about this forum is that its members are very fond of using metaphors and figurative language to deliver advice. This makes it hard to interpret and leads to confusion. I'm about to give you clear instructions, which will lead you to getting laid.
I'm going to assume that the girl in question isn't ice cold as I'm against trying to pick up strangers when you could just pickup through a social circle and avoid all the awkwardness and superficiality of a one night stand.
Linking
Alright, you're on a first encounter and the first concept you need to exploit is what I call linking. If you go to the same school, swimming club, gym, bar - you're linked. If you have the same friends - you're linked. Even if you have her added on Facebook - you're linked. Social people know how to use this to instantly build comfort and rapport.
It works like this: "Hey, you're Robert's sister. I think you were in the year below me. Yeah? I love that bar. I think I saw you at McDonald's the other day." Link as much as you can in early conversations. This is why cold approaches are so damn ineffective. The girl is ice cold because you aren't linked to her in any way.
Target Her
This should be a pretty obvious one, but in group conversations, you mainly want to concentrate on her. Give her more interest than you give others in the group. Ask her personal questions like where she grew up. Soon enough, you'll be in a one-on-one conversation with her while the group watches and tries to join in.
You'll notice that as you give her more interest, she may accidentally bump into you and even subtly move closer to you when you're talking to the others in the group. The trick is to give her some interest then go back to group conversations and keep shuffling back and forth - I think you guys call this hot and cold.
The more time you spend with her without physical escalation, the more likely you are to be her best friend
It is much easier to start from scratch with a new girl than to try seduce an old friend. You better be touching her from the very start and escalate as fast as you can in order to avoid her seeing you as a friend.
This is why the first encounter is so important. She doesn't need to know how you were before she came on the scene. You have a clean slate with her on the first encounter. You can be anyone you want to be and she'll accept it as you because she doesn't have any thing else to go by.
With that being said, you can now be a flirtatious guy and pull all of the following off.
Ask about her jewelery while picking it up. Touch her tattoos and ask why she got them. Play with her hair and mess it up. Pull out her hair ties. Shoulder barge her playfully when you're walking. Punch her arm when you're teasing her. Kick her lightly under the table. Pull her bra strap back and flick her. Slap her bum when she picks some thing up or stands up. Bump your knee into hers to emphasis a point under the table. Thumb wrestle her and cheat. Brush off cobwebs from her shirt. Fix up her clothes when her bra strap shows. Give her a massage if she has sore shoulders. If she hurts herself, kiss her wounds. If you spill some drink on yourself, wipe it on her. If she wears makeup, lick it and try mess it up. Play with her piercings if she has any. Hold her hand under the table. Slap her knee for emphasis. Push her lightly when she teases you back. Lean your head on her's exclaiming you're tired. Sit on her lap. Cuddle her. Stroke her hair. Squeeze her belly and blow raspberries on it. Kiss her neck. Nibble her ear lobes. Poke her in the side. Tickle her. Crack her knuckles when you're bored. Play footsies under the table. Draw on her. Throw leaves at her. Have private conversations with her by writing texts on your phone, passing it to her to get her to write back (awesome way to flirt).
Just to give you a few ideas and at some point, you need to escalate to holding her hand or putting your arm around her while walking. Doing all this kino in a flirty way should enable this to happen easily.
Conversation
All you need to do is ask her lots of questions. I'm not joking. Just move the questions to old boyfriends and tease her. She'll soon be imagining what you're like as a boyfriend.
The Kiss
After progressing to holding her hand, whether under the table or not, you're now ready for the kiss. If you're walking with friends, walk slowly with her behind the group and simply grab her shoulders to get her to stop. Kiss her quickly - no tongue - and keep walking. To break the aftermath awkwardness of the spontaneous first kiss, all you need to do is comment on it. A simple, "You taste good," will do the trick. The silence after the first kiss is a big no-no. You don't want to start a potential relationship without being able to be vocal about sexual stuff. Remember, you can be anyone you want on the first encounter.
The Make out
Obviously you need to isolate her for this. However, if you managed to get a few kisses in infront of her friends, this probably won't be necessary. There are many ways to isolate, but the most simple is to ask her to come for a walk.
If you're alone on a first date, getting to this point is easy. If you're at a bar, ask her to come for a smoke even if she doesn't smoke. Some times you get some resistance when you're trying to isolate. Don't worry. This resistance is normally in the form of "Why?" in which case you just tell her you're enjoying talking to her and you want to continue.
You can also break her away from her friends by going to the bar with her to get refills. Another one is "Come here. I have some thing to show you." Then you just show her an amusing video on your phone. Ideally some thing funny or shocking. Finally, if you're feeling ambitious, "Come here I have some thing to tell you." Then you tell her she's cute and you want more kisses.
Sexual Escalation
After the first encounter is over, you'd want to start making after plans.
"What're you doing later? Yeah? Come back to mine and we'll watch movies." What ever works for you. Don't be discouraged if she simply wants to go home to bed. All you have to do is invite her over one night for drinks and you're in. If you're a lonely teenager, parties are great places to facilitate sex. Sleep overs are good too. Hell, "Let's rent a hotel room and stay up all night," some times works too.
Sexual Escalation is making out with her and teasing her sexually. I'll give you examples in the same way I taught you kino.
Kiss her every where. Her lips, neck, ears, checks, cleavage, nipples, belly, outer thighs, inner thighs, slit. Alternate between tongue, biting and sucking. Don't forget to use your hands. Play with her hair. Put your hands under her shirt and rub up her sides. Never go straight for the nipples or slit without copious teasing. As in get close to her lady parts, then skip over them or feel her boobs, but not her nipples. When the making out heats up, you have a few options.
You can dry grind her for a bit. Take off her shirt. Take her bra off or finger her. Any of these things will lead to sex. If you meet resistance at any point, try a different option or go back to making out. As far as fingering her goes, I recommend felling up her bum then going from behind. You're much less likely to meet resistance doing it this way. If she's not wet, go back a step. Fingering a girl is easy. The vagina is at the bottom of the slit. The **** is at the top. Stroke up and down the slit making the whole area wet then simply stroke the top area of the slit and you'll get the **** no matter what. Alternate things by teasing her, fingering her vagina and dry humping.
Transition
Get her nude and yourself then sex will just happen. Start off with grinding. No penetration. Don't worry about putting a condom on - it's awkward and stops the escalation abruptly. Go to put it in and she'll either stop you and insist you wear a condom or you can say, "Hold up," and quickly put it on.
Good luck and I hope I provided you guys with some practical advice. .