This is a bad image, but it’s also bad copy, so no big deal. 
It’s a screen shot of a LinkedIn post from a contributor whose material I usually enjoy reading. But this post has all kinds of wrong going on, the most egregious error being the headline. (In fact, it’s so far removed what this author normally posts that I’m willing to bet it was created by a different writer.)
Let’s forget for a moment that “10 Secrets to Control Your Boss” is ultra-cheesy, and concentrate on the fact that it makes no sense. Acceptable alternative headlines that would make sense include:
- “10 Secrets to Controlling Your Boss”
- “10 Ways to Control Your Boss”
- “10 Tips for Controlling Your Boss”
And while “10 Secrets That Can Help You Control Your Boss” is horribly clumsy, at least it makes sense, and doesn’t lead you to think you’re about to read an article dispensing tips on hypnosis.
(The article itself isn’t about controlling your boss. It’s about how to get your boss to like you. So the best headline by far — sticking with the “X secrets” format — would be: “10 Easy Ways to Impress Your Boss.”)
I can’t just ignore the first sentence of the lead-in.
“I am a HUG FAN of controlling your BOSS!”
Aside from the typo, eye-roll-inducing use of caps and unnecessary exclamation point, what I really want to know is how does the author know my boss, and why is she such a fan of controlling her?
Common Sense & Logic 
Do you ever aim for a word limit when it comes to writing headlines? Or any general ideas?
The length of a headline will always depend primarily upon the medium. And there are very few rules that can’t be broken in certain circumstances. If you’re writing for a medium that has established best practices, that’s your first go-to resource. But then there are other factors to consider: topic, audience, clarity. Generally speaking, fewer words is (almost) always better, and that includes body copy.