Germans put truth and directness before diplomacy, believing that the fact is the important issue and that personal emotions should not deflect the truth from being spoken.
This directness can be interpreted by certain cultures (U.K, Japan, Korea etc.) as rudeness. It should be noted, however, that direct speaking is seen in Germany as a sign of respect and a fundamental in the search for the correct answer to a particular problem.
This directness in communication style also manifests itself in a lack of self-deprecation and coded language. A charge of arrogance is sometimes levelled at German businessmen and, although there is great pride taken in German achievements, this perceived arrogance is more a misinterpretation of direct speech. Germans will give a factual rendition of their own capabilities, which is not the same as arrogance. You can generally take a German at his word on these matters whereas certain other cultures will be far vaguer in their use of language.
Much is made of the lack of humour in evidence in Germany. It is certainly not true to say that Germans lack a sense of humour. As with all cultures, they have a highly developed sense of humour. The differences lie in positioning and style. There is a time and a place for humour in Germany and its place is not so much during the serious business of business. The more serious a situation, the more seriousness is called for. It is also important to remember that humour does not always or even very often travel successfully. What is funny in one culture can come across as nonsense in another.
Presentations are expected to be supported with a lot more specific detail than might be felt necessary in countries such as the US or the UK. Lack of supporting detail can severely weaken the credibility of an argument.