Good theory is based on information gained from practice. Good practice is based on carefully worked-out theory. The two are interdependent. (Larson l991, p. 1)

The ideal translation will be accurate as to meaning and natural as to the receptor language forms used. An intended audience who is unfamiliar with the source text will readily understand it. The success of a translation is measured by how closely it measures up to these ideals.

The ideal translation should be…

Accurate: reproducing as exactly as possible the meaning of the source text.
Natural: using natural forms of the receptor language in a way that is appropriate to the kind of text being translated.
Communicative: expressing all aspects of the meaning in a way that is readily understandable to the intended audience.
Translation is a process based on the theory that it is possible to abstract the meaning of a text from its forms and reproduce that meaning with the very different forms of a second language.

Translation, then, consists of studying the lexicon, grammatical structure, communication situation, and cultural context of the source language text, analyzing it in order to determine its meaning, and then reconstructing this same meaning using the lexicon and grammatical structure which are appropriate in the receptor language and its cultural context.

source: http://www.seasite.niu.edu/trans/articles/Translation%20Theory%20and%20Practice.htm