I like using the Rental Market Reports published twice a year by CMHC because they drill right down to zones within major cities and they also isolate suite types (1br, 2br etc.) and show average rent within that so you can roughly compare to your properties:
You can also talk with real estate agents in smaller communities where CMHC doesn't publish. In bigger communities the agents will refer to the CMHC, but in small cities or communities you need an agent who's experienced in the rental market.