Language and technical documents

What is the connection between language and technical documents? You could say that language is everything. Let's narrow the focus a little bit.

How do we know what language to use for our documents? As a novice tech writer, how would we start? Would you model your writing after the existing documents? Would you solicit feedback from users of your documents? What does Barker say about this topic in Chapter 12?

How about the question of amount of language? Should we be wordy or should we be tight with our words?

Is this document making appropriate use of language? What would Barker say about the language use in this document?