I often use polls near the ends of hubs and make one of the options "I'll share my experiences or thoughts in the comments below"... It works well for getting people to interact.
Also, you can do your finishing paragraph or even your opener with a question. For example I might open with a question as a hook - "Have you ever wondered why....." Go through the main content that answers the questions and solves the problem then at the end ask "So what do you think? Do you think (solution or answer) would work for you? or what else would you suggest? Feel free to leave a comment. I love to hear your thoughts .... something along these lines.
You have to invite people to participate and do so in a way that makes them want to - "call to action" - tell them to do something and they usually will. It's a marketing tactic. :)