There are many aspects involved in writing a good hub. First and foremost, your hub should be rich with information, description and fact. Try to fill your hub with enough detail that the reader can "see" what you are talking about. You are looking to draw the reader in so they want to continue reading.
Now add pictures and/or videos to further illustrate your point(s). The old saying, "a picture is worth a thousand words" is true to a great degree. Pictures and videos add a depth to your hub that helps enrich your hub and hold the reader's attention.
Pay attention to your spelling and grammar. Nothing breaks the flow of a good read more than incorrect spelling or bad grammar. Concentrate on the flow of the article. Does one sentence run smoothly into another? Are paragraphs short and easily readable? Is the thrust of the article laid out in an easy-to-follow manner that does not confuse the reader?