In many or most cases I like to look at two translations: one that stays as close to a literal rendition as possible while accounting for differences between the idioms and conventions of the language and the other that is faithful to the spirit and flavor even if it has to take some liberties with literal sense to create a similar feel in English. The difference is especially important when the language contains symbolism, metaphor, and other poetic devices: to convey the same effect in English, it may be necessary to choose parallel but not identical phrasing or use different figures of speech.
When the original is highly literary, beautifully written and not just prosaically businesslike, I want the same flavor in a translation. For that reason I sometimes choose a very old translation, like from early in the 20th century, even if it doesn’t reflect the latest scholarship.
When possible I like to see a translation alongside the original, on facing pages, even if I can’t actually read the original—for example, if it’s in Sanskrit. It’s amazing how much additional information you can extract from text in a language you don’t know, and even in a written form you can’t read, when there’s a translation beside it.
I also prefer a translation that includes some words of the original, either in the body or in footnotes, especially for key terms and terms that could be translated in several (possibly controversial) ways. When you can see, for example, that the author uses the same German word in two phrases for concepts that might be differently expressed in English, it tells you that there is a close relationship between them. You can also look them up in a German dictionary and see how many possibilities the translator had to choose among; different translators may feel that different choices are correct, and we can be misled when we have our own ideas about the English word.