Some basics: Allyouneedtocreate a facebookprofileisan email address You can onlycreateonefacebookprofile per email address. It’s simple, seehere: http://www.wikihow.com/Create-a-Facebook-Profile
Facebook & Privacy Facebook offer lots of help on how to protect your privacy: http://www.facebook.com/help/?page=419
Being a member of a group If, for example, you would like to participate in a FB group, what does that mean for my privacy? Can people who are in the same group as I am see more of my information? When non-friends are in the same group as you, this does not allow them to see any more of your profile information than your privacy settings allow.
Being a member of a group (II) You can have as many facebook profiles as you want (remember that each profile will need a different email address) so if you want to keep the private person separate fom the public one (in this case, being a member of a group for professional purposes only) all you have to do is create another ‘profile’ specifically for particpating in said group.