Things to Consider when Learning Languages for Business
Speaking language for business is fundamentally different than speaking casually: to arm yourself for a business transaction in another language, consider these points of difference:
The most obvious difference is in the vocab range: business has a specific set of words, concepts, acronyms and ideas that are unique to it; indeed specific fields, sectors and industries will have their own lingo which needs mastering. Thankfully, many business-specific words are directly imported from English (including most acronyms). Some languages however (particularly French), have their own words and acronyms, which can create confusion.
It's worth noting that business relationships in other countries may be more formal than they are in the West: indeed, different types of business require different degrees of formality. In Japan, for example, there are a suite of formalities - linguistic and cultural - which need to be adhered to. As a general rule, the tone of business-speaking is of a higher register than casual conversation. Be sure to acknowledge the differences. A basic example of this is what 'title' you give your business associate.
Syntax and constructs
Just as business language requires a different suite of vocab, it also requires syntax that you might not regularly use. For example, it is perfectly possible to get by in a country without dealing with big numbers and even basic mathematics: two things that will no doubt crop up in any business conversation. Make sure you have a command of both, i.e. know how to structure and express these concepts correctly. Make sure to also master how to express time, place, statistics, percentages etc.
Don't forget the small talk too!
Ultimately you are two human beings talking to each other, so don't forget the human side language too! Learn how to express your hobbies, interests, favourite music/sports etc. If you find common ground with your business associate, so much the better.