What are all the pre-requisites for posting in a 'Foreign Currency'? | SAP-FICO

The following are the per-requisites, you need to take care, before posting in a foreign currency:
•    Local currency already defined for the Company Code (in the global parameters)
•    Foreign currency defined in the currency code Table
•    Exchange rate defined for the foreign currency and the local currency
•    Translation Ratio maintained for the local and foreign currency.