Facebook uses an algorithm called EdgeRank as Heikki has written about earlier in How do you get seen in Facebook’s newsfeed? EdgeRank determines what is displayed in the newsfeed. This is a combination of the factors: affinity, weight, and time decay.
Affinity means the quality of the relationship between the content creator and viewer (how often the consumer has liked posts etc. )
Weight means the importance that Facebook gives the content, if it’s a link, a like or comment etc. Comments are more unusual so they are given more weight. If you start a discussion around a certain topic, this post will be given much more importance than only a post with a few likes.
Time decay means the time that has passed from when exact post time. Older content is considered less important.
Post more often, create conversations, and make sure you track your posts to gain valuable insight to improve your results. Look for tips in Heikkis blogpost How do you get seen in Facebook’s newsfeed.