Click on someone's profile and on the right hand side you will see a list of options. At the bottom you will see the option to follow that user. click it once and you will be redirected to a page where you will be given the opportunity to leave that user fan mail. Refresh their profile and you will then be a follower. You can see this in your recent Hubtivity by clicking on your own profile. You can get notifications to your e-mail when the person you are following publishes a new Hub.
Hope this helps!