Part 1 here. Many more parts will be along in due time.
Is the ordinary person a monoglot or a polyglot?
Does every cultural group have its own unique language?
Do any subcultures within the larger group speak a different language? (i.e. acrolects, jargons, etc.)
What languages did people speak in the past?
Are these languages preserved in any way?
Which languages have writing systems?
Are the writing systems alphabets, abugidas, abjads, syllabaries, hieroglyphics or semasiographic?
Which languages share orthographic systems?
Does any language have more than one orthographic system?
What materials are used to write the language?
Who is literate?
How do they become literate?
What dialects does a language have?
Are its dialects mutually intelligible?
What cultural associations does a dialect have? (i.e. rustic, slang, etc.)
How do non-native speakers learn the language?
Which non-members or non-native speakers are most likely to know the language?
Why do non-native speakers learn the language?
Wikipedia's article on constructed languages
In the Dawnlands, most people are at least badly polyglot. Characters have all Language (Other) skills at a starting percentage of their INT, and speaking a related language or dialect to one's native language is +25% to the test, giving most people a passable chance to get their point across.
Monstrous Elvish (the Kaddish name for the language) is the oldest language with a writing system, known as One Claw. It is believed to have been invented by a gnoll who used the claw on his index finger to make marks on wax. More elaborate letter forms exist, up to the highly stylised Eight-Claw used by gnollish scribes in the Cities of Night for official documents. The claws in question are often carved or engraved, especially for writing on paper. A thin ink-groove can be used to identify the corpses of prominent gnolls from ancient times, as can an examination of the specific styles. Some of the Cities of Night were known to operate scriptoriums manned by the severed, undead hands of former scribes for mass copying. The chief scribe would use a glove sewn with runes of command, mimicking the motions which the hands would follow en masse. This was adapted into a weapon of war during the last desperate days of the Wars of Dusk and Dawn though most of the gloves and hands were lost when the Cities of Night were destroyed by the Kaddish.