Hi there,
A couple of golden principles to consider before promoting through Facebook (just my own 2 cents):
1) PPC has a much better conversion rate than promoting to your fans (regardless of how targeted they are)
2) A L W A Y S ...send prospects to a preselling landing page and not directly to the vendor's page (unless he/she's giving their product for free and in this case why should you promote in the first place? Well, there's an answer to that as well, but let's stick to the point).
Third rule: collect emails
Fourth rule: collect emails
Fifth rule: collect their...(you got my point by now...I think).
Mike.