You can see this by activating the “counts” on the front end (under question 4 in the USM plugin, question 5 in the USM+ plugin).
If you like to know when people start to follow you by email, then you can get email alerts from SpecificFeeds. For that, please claim your feed (see question above).
We are also thinking about implementing more comprehensive statistics for shares & likes as part of the Premium Plugin. Please let us know there that you’re interested in this feature, so that we know there is demand.