Let me talk briefly about how to be a good interpreter.
Obviously, you must be bilingual. But this is not enough. You also need to have good knowledge of the subject you are interpreting. For example, if you are a tour guide interpreter taking foreign tourists around to shrines and temples, you will need to know about the history of the shrine or temple and the gods and buddhas worshipped.
You may have to also explain about a famous festival held by the shrine. All this knowledge can easily be gained by reading a book about the shrine, temple, etc.
If you’re Japanese, you can read this information in Japanese and soon become knowledgeable about the subject. However, this is still not enough. Next, you have to figure out how to say it in English (or any other foreign language you’re interpreting in).
How do you do this? The best way is to read a book in English about the same subject. Then you will see how various Japanese terminology is translated into English. Ultimately, you have to study the same subject twice, once in Japanese and once in English. Yes, this can be time-consuming. However, it is very effective and you also learn a lot too.
Note that the English book you read must have been written by a native speaker of English, and preferably published in an English-speaking country. Don’t read or rely on the English tourist pamphlets published by Japanese tourist associations. The English in those pamphlets are only translations of the Japanese and often not a very good example as English.
In the case of religion, there are many common words like 神棚、鳥居、菩薩、地蔵。Some words have English equivalents, but often there are none. In such a case, you can either use the word as is in Japanese (such as “torii”) and explain it, or add a descriptive English word to it (such as “torii gate”).
A word like 神棚 can be translated as “household Shinto altar.” Some dictionaries call it “household altar,” but this is not good because it does not indicate the religion (Budddhist or Shinto). 神棚 is definitely Shinto, and 仏壇 is “household Buddhist altar.” If you only say “household altar,” it could be either Shinto or Buddhist or whatever religion.
So study hard and do a lot of reading, in both Japanese and English (or the foreign language you’re interpreting in).