In some ways, Facebook ads are just like other pay-per-click systems, where you compose a message, make a bid, and look at the results. In other ways, however, they represent an entirely different animal, since you have to target by customer types and demographics, rather than keywords.
Although the executives at Facebook would like you to think that changes everything, the truth is that you should probably approach Facebook advertising the way you would any other PPC effort, with a couple of small tweaks:
Start smaller, but give your Facebook campaigns more room to grow. Not only is the service new, but it’s still evolving. That means you shouldn’t devote huge money to it right away, but also that you might have to be more patient in your approach.
Allow for a longer sales cycle. Because you are targeting a certain kind of customer, rather than waiting for them to search a certain keyword (like a product name), the emphasis has to be more on building interest than it is on generating quick sales with urgency or low prices. Track your results over a longer time frame to see if things are paying off.