I've been teaching in public all-girls middle school for the past 6 months and am still working on this with my students, so probably there are people better able to answer this than I am, but I have nothing to do today so I'm gonna try anyway 

Number one recommendation, is learn their names. I hear from my students that they always get English names in their hagwons (I almost  never use my student's English names if I can help it, and only a handful of mine have them anyway.I think the whole idea is silly, but I digress). So learning their English names might be easier, but if you are able, try to learn their Korean names as well, because they definitely will have a deeper connection to their Korean name where an English name might just be more fun and frivolous.

Having strong classroom management skills is really helpful and important. Which I guess is obvious for teachers, but it does actually affect how well your students like you. I teach in two schools, an elementary where my co-teacher does most everything and then the middle school where I am in charge of all my own classes. I have a much better rapport with the middle school students because they see me as the authority figure. I use a point system, so that way I can take away points if they are being unruly and give out points for class participation, and then the groups that have accrued the most points win a prize - usually a piece of candy. Middle school girls adore candy and snacks of any kind. I don't know how much leeway you will have with this in hagwon either cause I've never taught in one, but Korean kids are HIGHLY competitive and they love games and any chance to compete with and squash each other.

Also, ask them questions. Be genuinely interested in their lives. This works better with higher level students, but my low level girls can get into this as well. I make it relevant to what I'm teaching. Like, a few weeks ago we had a some random thing in our textbook about introducing people with "His/her nickname is..." "His/her favorite food is..." "He/she has a pet..." And I asked if any of the girls had pets and then spent some time finding out what all their pets were. It did not involve using any of the target language and really very little English skill at all (they just give one word answers mostly like "dog" "cat" "fish" and so on.... lots of my students have fish lol), but giving them a chance to tell you something, ANYthing, about themselves and their lives will make you feel closer to them and vice versa.

Korean kids hit each other a lot. That's totally a thing. I've seen a lot of people making rules about no hitting in their classes or complaining about this in a general sense, but just let it go. Unless someone is really being hurt or upset, just let them be. It is not abnormal here and most of the time it is all in good fun and they will be more comfortable and happy if they aren't trying to conform to a Western standard of behavior. I make no comment on the appropriateness or preferability of this behavior in the West versus Korea, not trying to start a culture argument, but in Korea they don't care about kids hittsing each other so just let it go.

This is already longer (and probably less helpful) than I intended, but one more thing. I definitely don't recommend trying to force pop culture references (like Kpop bands or hit dramas) that you are not yourself interested in, but I think it does pay-off to have at least some peripheral awareness of the things that they care about, so you can pick up on references they might make, which will really impress them. But definitely don't try to force it.

I am still learning how best to work with my girls and improving always, and I do have the benefit of  being female and in my 20's which helps. Just remember that middle school is a really tough age, especially for girls, and I think even more so in Korea with the enormous pressure they are under in school and also  that by the time your students get to you, they have already been studying all day in their public school and they are tired and over-worked, so if you can remember those things and be sympathetic towards your students it will go a long way. A big part of building rapport is whether you actually like and care about your students as the little people and future adults that they are. 

All excellent points from Maddragonqueen, definitely showing an interest in the students and that should be a base for teaching everyone. 

Like her I taught in a girls middle school last year and found it to be one of the best schools I taught in.  Even though there were 1000 students in total, this meant classes of 36, which kind of inhibited certain activities.  I know you will work in a hagwon so it will be a bit different as in public school we have a lot more contact time with students outside of the class (lunch time/break time/extra classes etc)  But like Maddragonqueen said learning the names is really good.  I have the same problem that I gave up with the English names long ago as it is pointless, especially if controlling a class.  Find out the students names, maybe even make some name cards for them and decorate them and they go on the desks in front of them, this will help you put names to faces.  Make folders for them to keep work in too.

I am not exactly the coolest person (years ago maybe) but I try and talk about things with the students that they understand, even though I hate Korean TV with a passion and K-Pop.  Maybe talk about Korean dramas or some music things, then you can get some connections.  Also learning a bit of Korean will go a long way, that can help the lower level students and you can talk a bit with them on that level.  But don't worry about making mistakes, they will find that funny, and probably then help you too. 

I think understanding the students is a big thing.  Showing respect to them means respect comes back.  I can say that after 9 years here and all levels taught, but that can be almost a life mantra too.  Think before jumping in or scolding or shouting, girls tend to be a lot more sensitive and will remember something you did a lot longer than boys do.  Teenage girls are going through a lot and as they go through middle school they are getting more and more pressure from parents/teachers to go to the good high schools.  But I found after teaching only boys and now only girls that girls are by far the better students to teach.  I am not sure if it is the gender inequality in Korea but i find that boys are molly-coddled more by their parents and they are much lazier.  My wife now teaches at a high school which has segregated classes for the first level.  As I now teach at the girls high school we have our exchange of opinions.  At the end of my class my students clap.  My wife told me that when she finishes her girls class the students always have a great reaction and are bubbly.  The boys? well, the boys just get up and file out.  Not all boys mind you.

Think before jumping in or scolding or shouting, girls tend to be a lot more sensitive and will remember something you did a lot longer than boys do.  Teenage girls are going through a lot and as they go through middle school they are getting more and more pressure from parents/teachers to go to the good high schools. 

This is a REALLY good point and something I didn't think of because I naturally do not scold or shout much (unless to be funny  ) but this is very true of girls this age.

To help remember names (since I also agree it's very important to build rapport)
- SEATING PLANS. Holy moly these go a long way.
- MNEMONICS (any way you can) AND WRITING THEM DOWN. (E.g., an easy one: I have a student named Song Shin. 2 English words).
- I also have a memo pad in my phone where I organize it by class and write down their names and hints (e.g., Yoon-ho: the one who got suspended, You-min: the one who likes Ukrainian girls). These are all real things.
- I had no idea the school had a chart with photo/names of the students. I'm sure each school has one, so get your hands on it and take a picture of it!

Think before jumping in or scolding or shouting, girls tend to be a lot more sensitive and will remember something you did a lot longer than boys do. 

Yeah, this. I hate teaching middle school girls for this reason. If you get a motivated class they can be great but if you scold the wrong girl then it can ruin the whole class. It's like a hive mind that never forgets.

  But I found after teaching only boys and now only girls that girls are by far the better students to teach.

I'm going to say the opposite. I much prefer teaching middle school boys in a single sex class. Mixed class, not so much.

Out of context, the title of this thread is a bit creepy.

Out of context, the title of this thread is a bit creepy.

Honestly....Kpop and candy!

Familiarize yourself with some kpop boy bands (Seventeen, BTS and iKON are the popular ones right now) and ask them which is their favorite member. They may even ask you which guy you think is the most handsome.

And candy for good measure...everyone likes candy. I've taught at a girls middle school for 2 years. Difficult to get through to, but not impossible.