Appreciating that individuals from different cultural backgrounds have different cultural customs, norms and expectations is vital for success in international communication. Interpersonal contacts could happen for private or business reasons and purposes, but intercultural communication is important in both cases.
Reading guides on cultural diversity could immensely help in establishing good intercultural communications. There are many guides and information available on the net and in libraries/bookshops. I have personally contributed to develop one of these guides, "How to speak culturese", putting my experience of an Italian living abroad in use for others. In cultural terms, those guides explain the best ways to make contact, host a meeting, enjoy a meal abroad. The knowledge of cultural differences is also important when meeting foreign guests at home. Nobody wants to offend others unintentionally, and these guides teach those little culture p's and q's.
Cultural awareness guides are also very helpful when communicating on the net, in forums, blogs and chat rooms. The internet is serving as an international communication medium; if you reach the rest of the world with your website/blog/message, your hope is that the rest of the world will then respond in some way, and you must be prepared to it.
Intercultural knowledge is also vital in business when creating a new brand name or logo. For example, Gerber, the name of a baby food maker, is also a French word for vomiting. Simple faux pas can sink you. Learning the customs and culture of a foreign country signals communication competence and shows a great respect for others. Culture speaks louder than words.