When can one create a "zusammengesetzes Nomen"? When should one use genitive or prepositions instead?

Answer 1

In general one should use a compound noun in German when a noun is being used to describe another noun that follows it. In other words, German doesn't like to use nouns attributively (in the place of an adjective) and instead will combine the noun being described with the noun(s) that describe it into a compound noun. In English, three nouns make up the following phrase: "helicopter landing place." Because the two descriptors are nouns and not adjectives, German prefers them to be compounded into "Hubschrauberlandeplatz." In such compounds, the final noun is always the one being described, and the nouns that come before it are the descriptors.