What makes a good translator? - Part 2. Language skills - the obvious part :)

I guess this is the most obvious truth about translation. If you are not bilingual, you can't be a translator. But you know what? I've met some people who honestly think that anybody can translate. Some even think that a machine can do it. You can read about one of such cases in my post called "A funny sad story". But even being bilingual doesn't mean you'll be a good translator. As one of my very respected colleagues once said, being bilingual just doesn't cut it. My post about proofreading explains how being bilingual doesn't mean you'll be a good proofreader. The same can be said about translation! I think it's not a secret that when you are studying a foreign language you also absorb a foreign culture and many idioms/concepts/grammar structures that are unique only for this language. And if you don't possess relevant training and/or experience there's a risk that your translations will not sound native because they will be too literal, they will have bad grammar (you can't imagine how often I edit the work of Russian translators who somehow think they have to preserve English grammar in their translations. I wonder who told them that Russian grammar doesn't apply to translated texts) and your sentence structure will be foreign as well. In the latter case the reader gets a funny feeling because all the words seem to be correct, but their position in the text is wrong or uncommon for native speakers, so the text sounds really weird.
My post "How do I work on my quality" has some info about how I make sure my translations are accurate and easy to read. How do you do it?