This is a great thread. I am glad to be involved in this discussion. I have found it does work best when I REALLY reward good behavior and punish bad behavior (as best as I can as a NT)
As for rewarding, I have a stamp system in place and those who participate in class and behave properly receive a stamp (I use my own stamp which I bought from Insadong for 5,000 won). And, as an extra incentive at the end of the semester I will pick the top 5 kids with the most stamps from each of my classes (I have 22 classes) and give them a certificate I printed off (from 123certificates.com) as well as choco-pie and an eraser or pencil (thank you Daiso!). Generally, the korean students are really competitive so they like this idea of competing against each other for stuff.
For my bad classes, I recently have had a bit of success making them sit boy/girl/boy/girl. First, I make all of them get up and the boys line up against one wall and the girls line up against another wall. And, then I hand pick how I want the students to sit boy/girl/boy/girl. I then tell them, "You act bad I will treat you like a baby and you will sit like this for the rest of the year, You behave well you can return to your old seats. Its completely your choice." And, I try to make sure I sit the really bad students in the very front so I can monitor them and control them via "the stare" which is where I stop class and stare at them until they stop acting horrible.
If they are extraordinarily bad, i.e. destroying the furniture, screaming in the middle of class, fighting, throwing pencils, throwing their shoes etc I stop class and tell them, " Push up position. Now." And, if they don't do that I then tell them, "Either you do the push up position, or I go visit the Principal right now. Its really your choice."
Its really hard if you have a co-teacher who doesn't do anything, but generally I have found if you tell the students you will visit the VP or Principle's office its very effective.