Overall

Try to maintain phrase-by-phrase (rather than word-by-word) loyalty to the source language, unless excessively awkward in English. Read the lines out to yourself. If they sound awkward or weird, try changing things around until everything flows smoothly.

Being literal is not necessarily the best answer, as long as the conveyed meaning is roughly the same.

Version of English

Use US English conventions as a standard (e.g. “Color,” not “Colour”).

Grammar

Try to avoid inverted sentence structures and passive voices as much as possible.

TL Notes

TL notes should be kept to a minimum and, when possible, inserted creatively at the editing stage (e.g. with pointers, markers, or images) rather than written out on screen.

Idioms

Whenever possible, try to replace Japanese idioms with English ones of similar meaning.

Wordplay

Try to localize wordplays to English. If the phrase is truly untranslatable, then localize it.

Emphasis

Use italics or subtitle effects for emphasis whenever possible.

CPS Guideline

CPS (characters per second) for a line determines the readability of the subtitles. This isn’t a steadfast rule, but when a line seems particularly long for the amount of time it appears on screen, the subber will probably come back to you and ask for a shorter option. Be proactive and try to keep this in mind during translation. Break up lines accordingly. If it’s obviously too long and you’re not sure what to do, then make sure you let the Proofreader know.

• 5-20 is ok. 10-19 is ideal. 20-24 is pushing it.
• 24+ is unreadable and almost always requires a rewrite.