When committing to the challenge that a Spanish to English translation represents, since we're dealing with such opposite languages, the use of an extensive and reputable dictionary is a key instrument. Luckily these days the Internet provides several sites that carry the best dictionaries in the world, which makes it even easier to work. Imagine the times when translators had to carry heavy books from one place to the other to fulfill their daily tasks.
Nowadays, websites such as wordreference.com, Babylon.com, dictionary.com and spanishdict.com are excellent tools that allow translators to research words, compare meanings, find synonyms and antonyms and even consult their forums where expert translators reunite to help each other sort out the meaning of difficult phrases and concepts.
Not to mention the fact that the world-wide web also has links to the best libraries in every country -most of them are free- as well as sites that contain the most renowned encyclopedias in the world.