Thanks to the 9/20/12 site update, from now on all general and specific episode discussion will go to the episode pages, where the Episode Discussion Stream (EDS) now exists. Those should be considered the official episode discussion threads, and the same rules apply. All general and specific discussion of an episode should go there. You can also reply to specific posts within the thread, generating sub-messages.
As an alternate, you can discuss the episode on the staff review page. Unfortunately there seems to be no benefit, and several harms, to dividing the episode discussion between three separate threads. Since staff has created two mandatory threads, that only leaves one left to remove.
If/when posting spoilers, please be courteous of other users. Only the most recent five posts will appear on the page, and all messages will drop lower on the page after the episode airs. Spoiler-news prior to the episode airing ("OMG - jimmydies.com just officially announced that Jimmy falls down a flight of stairs and dies two minutes into this episode!") should go here under the news thread.
There are apparently some limitations as far as putting separate paragraphs in the same post. You can paste in a paragraph return from a word processing application, or if you're replying to someone else.
But for now, EDSs are what we've got.