Despite what you might have heard (IE: That you just gotta target age, and go broad) in 99% of the cases, this isn’t true if you want to make money and/or don’t have an unlimited budget.
Laser targeting is very important, and it is what will help you get nice ROI on your marketing.
To laser target, what you have to do is first launch audience insights tool inside facebook manage ads.
Then set the geo, and leave everything else as is.
Now, if your interest is say Lord of the Rings, type that into interests.
Clicks on the PAGES LIKED tab inside audience insights, and sort by AFFINITY.
You want pages that have the highest affinity. These are the key to your success.
But, rather than just taking these pages and targeting them, what you want to do is open each, and check if they are REALLY related, because sometimes they will be not about your product/service you are trying to sell.
TIP: Look at when posts were posted, how many likes/comments each of them got. If the likes/comments ratio to total page likes is high, then you know this is a truly engaged FB page with a lot of passionate followers/fans.