You really need to be funny in your posts or at least have a little sense of humour. It can be forgiven if you are not funny, but what can’t be forgiven is not being able to find a way to make your reader laugh. Even a single “Caption this” photo is enough post to make people laugh. Try to include these.
YouTube has loads of comic videos uploaded daily. The YouTube Trend is a good place to discover latest funny videos. Make sure to make at least one funny post every day.