A good subtitle in my opinion should:
- bring to the target language all the information of the original without adding anything and without missing anything. (Note: all the information, not all the exact words)
- Adapt the language to the speaker's status, age, historical or geographical position, hierarchy relative to the person he speaks to...
- be immediately understandable to most people in the time provided to read it.
- be perfectly natural/fluent in the target language, as fluent as it would be if it were originally written in that language. No compromise on this.
How I deal with the following particular cases
Sayings, proverbs and expressions
1) If the segment is long enough and the overall dialogue is short, then I leave the idiom translated as it is with an asterisk and a note.
2) If the segment is short and there's a lot of dialogue, and I would risk going to three lines or more, then I just substitute with an English equivalent.
3) If the saying/proverb's meaning is obvious, I don't bother explaining.
Geographical and historical
Always explain with a note whenever there is space/time
I always leave the original. With a note if there is space/time
I would never translate "mandu" as "ravioli" in Italian, or kimchi as "sauerkraut".
Even in English, "rice cakes" is too vague. We don't know whether they are spicy or sweet, if they have sauce or not...
Korean word order
I always savagely change the order, and put the verb at the beginning so that it sounds like good English. You cannot compromise on this, and leave sentences like the following:
“This person, I will definitely do my best to protect”
"A long, long time ago, a man called Legendary Go Nan Gil lived".
"Director, so that you can travel on the path of righteousness, to tell you good things, isn't that my duty?"
Have a good laugh on this page: http://tvtropes.org/pmwiki/pmwiki.php/BlindIdiotTranslation/RealLife