let's take young men who like video games. So, rather than just target fans of MTV (I'm kinda looking old now I know), target men ages 18-24 who like 'Ghost Recon' or 'Diablo.' Just target fans of one game. That's it. Or, another example, target men or women who like 'Nascar.' Or who like a political or comedy show like 'Jon Stewart' or 'Colbert Report' or 'Conan O'Brian.' So, if you're wanting more female fans, then target women who like 'Jon Stewart.' That's it. Don't add Conan or Colbert. Also, I think most women prefer Jon Stewart. Again, this is why you need to know and understand your target audience. Also, if you know a YouTube channel or internet site where the viewers are a bit smaller and more targeted to your audience, then that's even better. So if want to target men who like gadgets, you might try using an interest of 'TechCrunch' versus 'Apple,' because Apple may be too broad, whereas TechCrunch is more narrow to a certain online tech-driven mostly male audience. If you're targeting people interested in SEO, then you might use the interest of 'QuickSprout' or 'SourcWave.' See what I mean. People who are really interested in SEO may have liked an SEO gurus fanpage. So find highly targeted fanpages by a guru for your niche, and then use that guru name as the interest category when you created your ad. So you're telling Facebook to only show your ad to people who liked that guru and this is as specific to their interests as possible. When people search how to make money online for beginners one of the most suggested way is facebook ads.
Here's a real example of mine. I understand not everyone's into religion and politics, but I am, so just bear with me. It's just an illustration, and a very good one to prove how using the right interest category for your targeted audience can greatly help you. And this is how you can learn to steal fans from a gurus fanbase :)

One of my fanpages targets the Conservative Christian niche. So I focus on middle-aged men with those views. And in the beginning I tried using interest categories like 'republican,' but that was too broad. It wasn't targeted enough. And my ads didn't get good click-thru results. Then I tried a guru in that niche Joel Osteen, but again too broad, and not specific enough. But then I saw a preacher on TV named John Hagee talking about politics and Israel. He's well-known enough to be a category interest in Facebook, but he's not so big that all kinds of people like him. In fact, he's very polarizing and a lot of people hate him. So he's actually perfect for my niche. And this is key for you. Polarizing figures who are both loved by some and hated by others can have very specific and loyal followers. So if you can find an internet show or author or band or political figure etc that exactly matches your target niche, then Facebook has already done all the hard work for you. Then this guru's fans can become your fans! All you need to do is promote ads to them.