Depending on where you live, there are a few different options on becoming certified. If you are in the United States, the most popular organization that offers translation is the American Translators Association. However, there are many translators that aren't certified so don't feel like they are the end all be all of translation organizations.
If you live in other countries, especially in Europe, there are governmental organizations that offer certifications and you'll have to search them out, depending on the country in question.
