First of all, make sure you write good and quality hubs. People like to read hubs that are good. Do a little research before posting to make sure the facts are good.
Secondly, earning money with hub is slow. You need time to build your reputation and traffic will build from there.
Third, basic thing is more traffic = more chance. Therefore, always remember to continue backlink and promote your articles in order to be successful.
Hope this helps. Feel free to drop me a question or visit my profile as I have wrote few hubs about how to make money as a writer :)