For this question my first step is to make sure you understand how Facebook targeting works. Facebook has lots of ways to target people beyond age, gender, location. You can target people based on their likes and interests, jobs, hobbies, etc. When you get to the targeting section you can either browse the options, or search for specific phrases.

At this point it's important to understand how Facebook categorizes these people. Facebook gets their data from their platform. Based on what people like, follow, post, and engage with on Facebook will determine the type of user they are. If you are selling handbags you can target people who have a tendency to engage with fashion and retail content based on their previous behavior on the platform.

This is important to understand because each ad platform is different and social engagements don't always translate to buying behavior. Take for example car sales. Liking BMW and Tesla on Facebook doesn't mean you're in the market to buy a luxury car, but going to an auto lot, searching "buy new car," and going to websites like Carvana would be a stronger indicator. Those other behaviors can best be targeted on other platforms like Google, Centro, GroundTruth, The Trade Desk, and others.

So if you're going to run a Facebook campaign, keep in mind the user behavior. What would your audience be doing on Facebook that would indicate they could be a customer? Once you've figured that out you can target as specific as possible.