This post on where foreign men can hook up with hot girls in Seoul for sex or dating will give you some tips but you will need to figure some things out on your own. Of course the biggest thing working against you is the language barrier. If you find yourself struggling with these girls remember there are plenty of female tourists around. Plus there are digital nomads or English teachers living here that will be pretty easy pickings as well.
Pick up lines are an interesting method on how to flirt with a girl. Because after all, knowing how to get a girlfriend is a skill that takes a long time to get good at. But do pick up lines work? Who knows? You might surprise yourself with how well they work.