Here are the spoiler rules for the TV forum. Once the show broadcasts on the East Coast, it's no longer a spoiler, so post away. If you post something before the episode in question airs, wrap it up in the SPOILER tags. If it's a long-term spoiler, wrap it up in SPOILER tags, and put a little disclaimer on it explaining how long it's a spoiler for. If you're on the West Coast, like I am, and you don't want to be surprised or disappointed, then don't look until after it airs on the West Coast, as the people on the East Coast will be talking freely (non-spoiler-tags) about it. -- Update
If your posting includes a link to an article that is relevant to the topic at hand, but includes some info that could be considered a spoiler by people that truly don't want to know anything even remotely connected to future episodes... If you think some people MIGHT consider it a spoiler, put it in SPOILER tags. If it could go either way, put it in tags, and make note in your post that it's SPOILERISH.
This should fall under the umbrella of iczorro's "if some people might consider it a spoiler" rule, but I wanted to spell it out. Anything in "Next week on [show]" or any other type of promo should be wrapped in spoiler tags.