False friends
Beware of words or phrases we call "false friends". These are words in the original source language which you retain in your translation, often because you cannot think of the correct translation. If you cannot think of the right word, how can you expect your reader or listener to? Of course, languages borrow from each other all the time. If a society comes across a new idea, it may simply use the foreign word without inventing a word of its own. Remember, however, that you are translating meaning, not words. If you come across a word in your original language which has no equivalent in the target language, perhaps you can use a phrase (i.e. several words) instead. For example, many languages do not have a word for "computer". Instead of retaining the English word "computer", can you translate it as "a machine which does brain work" or something similar? Be careful, though, that you do not try to re-invent the community's language to suit your own way of thinking. If you have problems with translating words, consult experts or ask your colleagues to see if you can reach agreement on the correct translation. If you are a journalist working in a small language community, the words you decide upon could become the standard usage.
Of course, some foreign words will inevitably creep into other languages. Words like "computer" are becoming widely accepted by speakers of non-English languages and may eventually be understood by everyone. The problem arises in the time between the foreign word being first introduced and it being understood by everyone. During such transition periods, use the word untranslated, but follow it immediately with a translation or explanation. For example, you might write in your target language the equivalent of:
The provincial government is to buy computers for each of its local offices. The computers are machines which will help office staff to keep accounts, write letters and do other jobs.