What are your limits? What are you okay with being out there? The companies that run these organizations are tracking you, and you should decide how much you're willing to give them.
Who are you willing to have see your profile? Different social networks serve different purposes, so decide beforehand what you want to make available to your coworkers, collaborators and students and what you want to keep separate.
Know what you have the right to do with your own work if you’re thinking of posting the full-text of anything to one of the networks. Check back in with your copyright agreements if it’s been a while since you signed them, or visit SHERPA/RoMEO (linked below) to see your publisher's copyright policy.