- Difficult jobs: Is someone other than a professional translator of that language having to do the job? Are you sure they heard/read it right? Was it done spontaneously or in a hurry? Translators don't always have the benefit of a neatly-printed paper copy and a week to do the job.
- Anything that sounds unnatural: Anything that you wouldn’t expect a native English speaker to say in that context might be worth a look. Translating the untranslatable often ends up clunky. This should be the first thing to catch your eye.
- Things don't match: Corresponding wikipedia entries, google images, people's reactions to the word, or even clumsy machine translations that mean something completely different. If native speakers aren't treating the word in the way the translation would imply, something's wrong.
- Tenses: English has a lot of choice when it comes to tenses. Most other languages don’t. Translators often have to editorialise via tenses where the writers of the source texts don’t.
- Idioms: It’s generally expected to translate an idiom into an idiom. Some idioms don’t translate. Often, an idiom about showers will translate into an idiom about eggs, or even stranger. Idioms also vary in register or usage: scratch your head if you see a typically political idiom used for cooking.
- Wordplay: If you see a pun, rhyme or any other kind of trick with the sound of the word, the translator may well have sacrificed part of the meaning to get it to work. This also applies to humorously appropriate idioms.
- Inspector Clouseau: Foreigners often don't sound very natural in English, not just because they haven't learned all of it perfectly yet, but also because they're having to think a lot harder than normal, and their brains are still at least partly set to foreignish. Translators also have to think very hard and switch backwards and forwards between languages: same problem. If the original speaker was not a cartoon Nazi or pasta chef, but sounds a bit like one at times, that's a bad translation.
- Foreign words: The very act of using a foreign word means different things in different languages. A lot of languages use French to sound sophisticated, Latin to sound scientific and/or English to sound businesslike and trendy. Sometimes the entire concept of a language requires translation. We also use concepts as shorthand for languages (pasta for Italian) and visa-versa (Cyrillic letters for Communism).
- Untranslated bits: Sometimes translators leave a word in the original language, knowing it will be understood, knowing it will have a specific effect or knowing it can’t be translated at all. Don’t expect ‘raus’ to sound fascistic to Germans or ‘paella’ to sound exotic to a Spaniard.
- If/When: This is one of the most expressive things we have in English. So much so we can cause huge offence with the wrong one and very often correct our own usage. Some languages don’t make this distinction at all, or may draw the line somewhere different to possible/certain. (Germans, for example use ‘wenn’ for likely and ‘falls’ for unlikely).
- Cultural/historical significance: Who could argue that the English and the French attach the same cultural significance to Waterloo or Agincourt? And don’t expect your own cultural practices to have the same resonance either – teatime and popular opinion on the Queen are very different in the imagination of foreigners to in real life.
- Genders: Some languages assign gender according to the word (Hebrew, Arabic, most European languages), some according to the thing (English) and some not at all (Farsi, Finnish). Some don’t even order it by sex (Navajo). While gender is largely grammatical and apolitical, think about whether you would call a tomcat ‘he’, ‘she’ or ‘it’ and who might use which for a transsexual.
- Food: Different countries eat different things. Even without the Americans we British can’t even agree what’s a ‘pie’ and what’s a ‘pudding’. Other countries don’t chop their foodstuffs up the same way we do, so don’t expect a direct translation every time.