From Poynter Online:
When reporting on the unfolding story of the election in Iran (and it's possible irregularities), Twitter can be a useful tool for getting real-time context about what's happening and what people are thinking and saying.
As journalist Amy Gahran has written before, hashtags (short alphanumeric "labels" prefaced by "#") are a key tool for following any topic, breaking or otherwise, on Twitter.
The leading hashtag to follow appears to be #IranElection. But far more people are talking about this issue than reliably using the hashtag, so it's also useful to search Twitter for these keywords: Ahmadinejad, Mousavi, (or Moussavi), Iran, and Tehran. (Hashtags and keywords are not case-sensitive.)
That's one hashtag plus at least four keywords (more if you consider alternate spellings). Quite a bit to keep your eye on. Plus if you use a column-based Twitter tool such as Tweetdeck, Seesmic Desktop or Monitter, you only have a limited number of columns to work with. (Each column displays the results of only one search query.)