Sharing on message boards (if they allow you to link your site......some sites are strict about that and consider it spamming) of a specific topic is a great way to increase traffic pretty quickly. Sharing your hub with friends on Facebook gives you good traffic as well.
The best tried and true method though is two fold. #1 A topic that doesn't have a lot of information out there. Do a quick Google search on a topic you are thinking about writing. If there isn't a lot out there, you may be onto something. #2 Once you know what you want to write about, go to Google's Adwords and use their keyword tool. That will help you identify keywords that people are searching for.
It will take at least a few weeks before the Googlebot picks up on your hub and maybe several months before it climbs up their rankings. But if it's a good hub with good keywords on a topic that is being searched for but doesn't have a lot of info on it......it could be a huge traffic gatherer for you.