I get this question a lot when I begin to describe the work of a bible translation consultant. In the current bible translation model, the translators are mother-tongue speakers of the target language. The consultant, in some cases, has no experience with that target language at all. It is the consultant's job to check the translation for accuracy to the biblical source texts (Greek, Hebrew, and Aramaic) and for clarity and naturalness in the target language.
So... how do consultants do this?
With linguistics.
I'm a Linguist!
Most people hear "linguist" and think that means Walking Human GoogleTranslate. A linguist knows nearly every world language - she's one of those universal translator devices straight from a sci-fi film! Quick! Say something in Klingon!
Sorry to disappoint, but the only language I can speak is English -- and in a crowded room of strangers, sometimes not even that. (Incidentally, I will also never say anything in Klingon. I identify with a different fandom altogether and my fingers can't even make that universal longevity sign. Sigh.)
Oh, I've studied a bunch of languages. I can read Classical Latin, Koine Greek, and Biblical Hebrew. I've had (limited) conversations in Arabic, Swahili, and Spanish, and completed grammar and phonology assignments on Tagalog, Malay, Mixtec, and Quechua. And though Klingon is beyond me, I may be able to greet an Elf should the need arise. But none of that is really knowing a language.
Linguistics is simply the study of how all languages work. Like other sciences, linguistics has many different specialties that attempt to answer various questions. What do all human languages have in common? What makes a noun a noun? How does this stream of pixels entering your eyes right now somehow get processed in your brain as letters, sounds, words, and meaning? How does the endless stream of noise you hear every day communicate ideas, thoughts, intentions and even deeper bits of humanity like hope, grief, wisdom, and love? How do these concepts differ across people groups? What makes a good story really good?
Discussing any of these questions at length doesn't win me any credibility with GoogleTranslate or help me get through an airport in Norway, but applied linguistics does help in translating the Bible.
Linguistics in Bible Translation
When a translation consultant checks a bible translation for accuracy and clarity, they use applied linguistics. Like any other science, applied linguistics is largely about solving a puzzle, finding out why things are the way they are and understanding them well enough to be able to replicate the result.
So translation consultants ask a lot of questions. Not the questions you'd learn in a foreign language class or type into your travel app - I don't ask anyone what time the next train is or how to get to the station (if I can help it). Instead consultants ask, "Why did you say it this way?"
Sometimes, consultants will ask translation teams to bring some samples of other stories, folktales, or songs in their language from outside the Bible. These are like field samples that show the language in its natural habitat. We can put these samples 'under the microscope' so to speak to learn how they behave and why. That's key information for making the translation sound natural too.
Other helpful tools are the back translation and interlinearizer in translation software. A back translation is done by a mother-tongue speaker of the target language who did not work on the translation (and therefore doesn't know what it should say). This person translates the translation back into English or whatever language of wider communication is used (Spanish, French, Portuguese, Arabic, Mandarin, Tagalog, Malay, etc) as literally as possible. The interlinearizer does the same thing via computer and usually needs a human corrector to comb through it for accuracy. (See, computerized translation devices aren't so swanky after all.)
The consultant can use these tools as an x-ray vision into the unfamiliar language, always with the translators' help, to see what's going on in the language. With these and the knowledge of discourse, syntax, key biblical terms, and the source texts, she can ask the right questions to improve the translation draft.
Study Linguistics!
So if you want to fluently speak every language in the world, well... good luck. GoogleTranslate has its own set of translation issues.
But if you'd like to study what makes human language amazing while having the opportunity to interact with the speakers or texts of hundreds of languages around the world, studying linguistics is a good place to start. It's also a great idea to learn one (or more!) of the languages of wider communication... you know, just in case you do end up needing directions after all.