Since businesses and professions have already been as globalised as the world economy, being intertwined with other countries is becoming a normal occurrence. It is because of this flow of information in and out of borders that makes business and commerce truly expansive nowadays. Of course, as a consequence of this expansion, we can only expect that the needs of different businesses and professions dealing with their industry demands also complicate. As part of this trend, cross border negotiation between different nationalities is becoming very apparent. This means that you would have to deal with foreign clients and talk to them about matters which may involve your business and services.
At the top of your list, you must be able to speak a universal language that both of you can understand. Strictly speaking, there are various universal languages that one may "speak". For some people it's music, for others it's sex. Since you can't bring London escorts to a conference, you will have to find some other way of communicating with your client. A universal language means that it's readily understandable and doesn't need further explanation if you try and engage a conversation or dialogue with a person.
Perhaps a discreet suggestion for an after hours meeting for your client with a Middle Eastern escort companion might be acceptable. In order to veer away from any gross misunderstandings with your escorts plan, choose the English language to communicate. Although this might differ according to the nationality of your client, it's the safest one you can try to speak to him with.
Furthermore, you should also know the culture from which he belongs. This means that you should research what turns him off and what buttons to hit more often. There are times when different nationalities have uneven interests that usually don't meet half way when it comes to transacting something. For example, predominantly nationalities that are from the developed nations would often consider the nature of the work as a top priority in any transaction. They would look into the specifications and if it can be done given the amount of resources that are available. On the other hand, most nationalities from developing nations would consider the budget as their top consideration.
Lastly, create compromises which will allow the best contract to manifest between the two of you. Sometimes, foreigners would gladly compare what you have to offer with what they usually practice at home. If you say that you can finish this certain transaction after a week, they'd usually say that back at home they can do it quicker. Remember that although this might be true, it may just be a scheme for them to get their way. Regardless, try to give him an overview at what you do in your country and what you practice as part of what you have to offer your foreign client in the context of your local industry.