How do you know if you have a good translation in your hands?
Because the text you have is precise, concise and clear.
What does precise mean? It means that the chosen terminology is correct. In order to know what you chose is correct, you need both experience and good research skills.
What does concise mean? It means that since the right terminology was used, you do not need to explain the terms. This is a two for one savings.
What does clear mean? It means that you cannot determine that the document was a translation, it sounds and flows naturally in the target language.