We can look at the source material and ask ourselves what translation choice we would have made and see what the translator decided—but only if we know both languages! However, we can probably find examples and explanation provided by someone else.
We can compare samples for style and decide what sounds more appealing. That could tell us which book we’d enjoy reading most, though it doesn’t tell us which translation sounds most like the original.
We can judge a translation based on the effect a novel has on us after we finish it, but that’s not helpful for choosing which translation to read in the first place. However, we can listen to other readers talk about the effect that the book had on them.
We can rely on the opinions of critics who are presumably in a position to know better than we are. The trouble is that whenever there is a new translation, critics tend to disparage the previous ones. There’s no point in issuing a new translation if there’s no noticeable improvement, so fault must be found.
We can judge a translation based on the translator’s background and experience. What’s the translator’s experience with the relevant language, literature, history, and culture? If the translator has done other similar work, that’s a valuable sign of expertise. If the translator has an obvious political or religious bias, that might be a problem…