For those of you willing to put a bit of effort into this I have the perfect song to play at a party where you have access to an acoustic guitar. It's not too hard to pick up but it's not the easiest either.
The song on guitar:
https://www.youtube.com/watch?v=4jgr6tBtJEw
The actual song:
https://www.youtube.com/watch?v=9yKk-3TD7tk
Play the song Damien Rice "I Remember." You don't need to sing but if you can that's great. This song is progressive, very easy to listen to and the perfect acoustic song for social settings. This makes it a great tune to just strum towards(strum random chords with no real direction then just break into it).
Learn how to play the song on guitar and use the intro(first two minutes) to talk to your target. Start off with a bit of info on the song or singer/songwriter. "Do you know this song?" "Ever hear it before?" "It's by an Irish singer/songwriter." Separate your sentences with silence as you talk to her. The whole point of engaging her while you play through the intro is to get her
hooked and focused on you as you play the song. This will essentially ramp up your attraction. When you get to the meatier bits of the song(Halfway through) she'll be all the more impressed by the complexity of the song. Speaking to her about the song is a good way to open and build rapport with her. She's interested in what you're doing and open to talking. When she listens to a nice tune she'll be more easily opened and feel more at ease with you because of the soothing effect such a song can have on her.
That's pretty much it. Just play the song and make sure you speak to her as you play. It's the perfect song to chat away to as you open up. After that you can offer to show her how to play the opening chords(Really easy) and work your magic from there. No matter what you do after that point she's all yours.
Other than that do as you normally would do in social settings. Talk to people, make sure people know who you are. Don't just be a douche and randomly grab a guitar and expect people who haven't a clue who you are to simply hover around you. If you don't make a point of talking to people and at least saying "hi" before this you'll just come across as the weirdo with the guitar in a corner. Open a few people, say hello then break out the tunes. Make sure you talk to the targets friends and they know you. If they go to you so will your target at which point you can passively talk about the song and cut the boring and tedious part of approaching and opening and skip right to building rapport and comfort as well as seduction. You're doing all three things at once here: Speaking to her and talking about the song is building comfort and rapport. Talking to her directly over everyone else is basically telling her you're after her so she has two options here: Make an excuse and leave or stay around the guy that's clearly hitting on her. If she stays(Which she will) you can close her with practically zero chance of failure.