When you want your target audience to take a particular action, including on Facebook, you must ask them to do it, according to a study by Dan Zarrella for HubSpot that explored how various call-to-action (CTA) phrases impact the engagement of Facebook users.

Take, for example, "liking" a post. Among more than 1.2 million posts from the top 10,000 most popular Facebook pages (ranked by number of likes), those that included the word "like" drove roughly 2 times more likes than posts that did not include the word:

Similarly, Facebook posts that included the word "share" drove more shares (as well as more likes) than posts that didn't include the word:

Asking a Question on Facebook

In separate research, Dan Zarrella explored Facebook posts in the form of a question.

Posts that contain a question tend to generate more comments; however, they garner fewer likes and shares than non-question posts:

Though posing a question can be a great way to gather feedback from Facebook fans and page visitors, it's may not be the most effective way to drive overall engagement.

Specific words also tend to generate more comments. 

For example, questions yielding "yes" or "no" responses such as "should" and "would," as well as multiple choice questions such as "which," tend to generate more comments than nebulous, open-ended questions such as "why" and "how:"

About the data: Findings are based on the analysis of 1.2 million posts from the top 10,000 most popular Facebook pages (ranked by number of likes), collected in 2012.