Below I will explain how I usually do when making subtitles, and some rules I follow. The programs I use is Subtitles Workshop (when transcribing) and Aegisub (for timing). I know Aegisub can be used for it all, but I don’t like the newer version of Aegisub, so I keep using an older version.
I mostly transcribe and time subtitles for dramas, If I translate, it’s either from Swedish-English or English-Swedish. I can also time subtitles in Japanese.
To begin with, I prefer to manually transcribe and time subtitles. Not ripping them. In this way I feel I have more control over the number of characters per line, scene changes etc.
Length of lines
One line shouldn’t be more than 37 characters long (this includes spaces), and when there’s a comma, change to a new line.
Generally I try to keep the font size around 30-34px for English, and 36px for Japanese so it’s easy to read the more complex kanji. Fonts I like to use myself are: Arial, Tahoma, Verdana. Nothing too squiggly.
Enough time to read and scene changes
The ending is a longer than the beginning, I’m doing this to give the viewer more time to read the subtitles. I try not to overlap the subtitles when there is a change in the scene (purple line), but sometimes it’s necessary to keep the subtitles visible a little longer.
If lines are close to each other, I will “connect” them. Where one line ends, the other begins. This will make the transition between different lines smooth.
If there is little time when two persons are talking and they aren’t saying that much, I will add them together like this.
– Is he here yet.
Last of of all run spell-check before making the final quality check.
And if you’d like to do further reading.
This is how I started out back in 2011, by watching this video.