Take advantage of the free reporting for your chosen social networks, or look for a free service online that will help you keep track. Facebook in particular has some great reporting within your business page that can be sent to you via email, as do some of the other networks (depending on the settings of your page).

There are also a ton of websites and apps out there (free and paid) that will let you access engagement stats for the different social networks. We can’t advise you on these specifically, but a Google search should help!