I'm not sure how much any network will devote to coverage of a single race -- I'm sure there will be a crawl -- but my guess is coverage will be in the context of whatever shows happen to normally be on. Anyway, in terms of what to watch for, there haven't been a lot of close races in Massachusetts lately, and the most recent state-wide race of note that might be informative is the 2002 Governor race, between Mitt Romney and Shannon O'Brien. There was no incumbent in Man (R) v. Woman (D), and the Man looked like a politician, while the Woman was forgettable as a candidate. The mood in the country favored Republicans. Of course, one major difference (and a lot of other things, I'm sure, that don't fit this glossing over) is that there are greater national implications in this current Senate race.
Going back to the returns from that race, Romney won with 49.8% of the vote to O'Brien's 44.9%. I chose 23 decently-sized cities and towns that at least vaguely mirrored that result, with the idea that, as returns come in, they can serve as a decent barometer for the overall election. For this table, I removed all votes for third party candidates and normalized to just votes for Romney and O'Brien.
Obama comes to town tomorrow, speaking at Northeastern. I'll be watching football.
The percentage is what Romney received. So, if these results are predictive, Coakley needs to do >3% better than O'Brien in each town in order to win.