Finally, subtitles are unusual in that we are listening to the Japanese as we read the English translations. This has a subtle but important effect. In the best translations, some of the rhythm of the Japanese is taken into consideration in the English wording. Of course, this is not a hard and fast rule, and there are many reasons to break it. Matching the diction of the Japanese to the English is, to say the least, difficult.
Translation is, perhaps, the biggest part of subtitling anime.
Well, huge, frankly. The time it takes to translate a thirty minute episode might range from two hours to twenty hours, the average maybe being around six hours, depending on the quality of the translation and the amount of dialogue in the episode. Yes, I said twenty hours. Shows such as Please Save My Earth are incredibly dialogue intensive. That means that in a 30 minute episode, there are on the order of 400-600 lines spoken.