The Auto Follow
module is a simple module that listens for new user signups and sets specified profile(s) to either follow the new profile, be followed by the new profile, or both.
Normally A user follows a profile by visiting the profile and clicking the FOLLOW button. The result of this is that that profiles activity timeline feeds will be shown in the followers timeline activity update feed so they can keep up-to-date with what is going on.
It might be desirable to have every new signup follow the main site admin by default or the site admin follow new users by default. In either case this is the module your after to auto follow someone.