How to Create Good Subtitles
2. Line length - When you are done, watch the talk without the sound. This will force you to focus on reading and seeing how fast you can read. If you fail to read a line twice then you should shorten it (another tip: make sure you can read the line and still have time to look at the video). This is very important because other people do not know the text like you do, and do not read as fast as you do, so they will need more time :)
Ways to shorten the lines:
a) Remove fluff which does not add to the meaning, for example: Err, Well, very, Anyway,...
b) Remove repetitions. If something is obvious from the context then there is no need to say it.
c) Break the lines differently: move part of a meaning to the next or previous line which is shorter
d) Compress two lines into one and double it. In TED player similar lines show without blinking.
e) Find shorter synonyms or find a more common, thus easier to process, synonym.
More tips here.
3. Literal translation Most importantly: Would a native speaker say it like you just wrote it, or would they use a different phrase to explain the same meaning? Does it sound natural? Make sure not to mimic English word order.
4. Punctuation Make sure to learn your language-specific punctuation rules. Make sure you don't follow the English punctuation by accident.
5. Line breaks Learn how to break lines here. Rule of thumb: If a line could be used as an answer to a question on its own, then it is good, if there is an element which does not fit then it should be moved.
6. Language specific errors Navigate to your language in the sidebar of this page and see if there is a list of common errors available.
7. Meaning Think: What does the person speaking mean? Is the message clear? Do I understand? Could I explain it myself?
8. Specialized vocabulary Do your research. Proper names are very rarely translated in a straightforward way. The easiest way to do it is to check the term in English Wikipedia and then navigate to your language. You can also try the KudoZ term archive, and ask a new question if you can't find anything in the available answers. Also remember that proper names (of people or places) may not be spelled the same way in your language as they are in English (for example, Istanbul in English, but Estambul in Spanish). To learn more about searching for terms, watch this video
9. Units of measurement Check if the translator converted them to the ones most commonly used in your language, for example. miles to kilometers.
10. Culture specific items: Jokes, names of products, companies, famous people etc... Make them easily understood for your audience by either explaining them. So, not must Mr. X, but Mr. X a businessman or exchange the name for a category, so "Wendy's" into a fast food chain. Jokes and puns should still be funny, even if you have to achieve it by changing them a bit, you don't want the audience to wonder why everyone is laughing.
11. Sound information - Make sure that the Sound information for the deaf/hard-of-hearing, like (Applause) or (Music) is included in the translation. Look at a few other talks to see the most common way people translate those items in your language (so that there is one translation of (Applause) in all the talks, not three different synonyms, etc.).
12. Style If the change you want to make is preferential and the original translation is just as good you should refrain from introducing it or contact the translator about it.