There are several ways of finding out what's going on in Halifax, as far as venues, gigs and other events. Of course there's the main daily newspaper, The Chronicle Herald, but for less than mainstream alternative gigs, or for notices of meetings, rallies, sales, and all sorts of things, you can check out the notice posts. There are about a half dozen scattered around downtown Halifax. These were built to attempt to stop people from taping and stapling notices to telephone poles and fences around town. People still do that, but it has cut down a bit on that.
Another way to find out what's on, including good listings for the clubs, cinema and galleries is the free and totally irreverent weekly newspaper, The Coast. You'll find this in stands and in coffee shops all over Metro.