Hey there,
The main ones we are studying in Crime Fiction for Extension 1 are indeed the Cosy and the Hard-boiled. You needn't really concern yourself with the others unless it's personal interest.
I will try my best to give you the conventions as I know them.
Cosy:
* A small group of (house)guests all close enough to have commit the crime; most, if not all have motives
* There is often a host and an accompanying butler/servant which hints at the upper-middle class in which cosy resides.
* Almost always located in a manor house or other enclosed setting, often a prominent history and described in flowery detail to hint at financial affluence and bourgeous values
* There is always a victim - often the first murder triggers subsequent deaths
* Crime often centres on money/death/financial dependence or liberation, or even revenge.
* The detective is not always a professional; often an amateur 'sleuth', or common person with a hobby or erking for snuffing out criminals.
* There is usually the prescence of red herrings, or false clues, set by the author to keep the reader guessing.
* Often is/often not working alongside the police in the investigation
* The sleuth typically possesses higher-class values and mannerisms, powerful skills of mental and rational deduction
* There is a denoument, which involves the gathering of all characters into a room for the final accusation.
Hard-boiled:
* There is a private detective, often world-weary, streetwise, resourceful, often with a history of failed relationships and a bit of a loner.
* The setting is invariably urban - dark, seedy, violent and presented in gruesome detail
* Often there is personal danger for the detective; although the PI is not often involved in his cases on a personal level, he (or she) is often in a position of imminent threat
* The sleuth usually is shown to be tackling the moral/social corruption around him as he is "morally superior"
* There is either one or a number of crimes which are also described in detail
* Realistic, rather than intuitionist
I'm sure what I have isn't definitive... if anybody can see something I've forgotten, please mention it for the benefit of the thread.
