I've seen some examples like on BlenderGuru.com and some other youtube tutorials. But, what would be considered the proper way to add a specularity map in cycles?
Do it just like blender guru. To do this see image:
To be more specific, Cycles is a unbiased ray tracing engine. That means that computer actually computes the rays of light in the scene. Because of this the specularity of a material is not controlled by a setting, but by the actual physical properties that create the effect. For this reason their is no specularity setting.
The reason why some render engines have a control for specularity is because they fake the effect.
I would use a mix node and connect the map to the factor input:
Also see these related questions: