Is your promotion campaign legal on Facebook? Do you ask members to like your page or your profile? What is authorized and what is not?
You need to be very careful and watch out for the risks. Your page could actually be deactivated by Facebook. You can actually get more info there.
To give you a good insight at what’s possible and what could actually lead you to a tricky situation, have a look at the infographics below, by Shortstack: