Write content consistently, make it original but don't expect oodles of traffic immediately. I have one blog over 10 years old based on politics, it has over 6K posts, plenty of comments and a PR of 7. That's the high side.
All my niche sites are done with Wordpress, you need good structure, use good quality images and relevant videos to engage visitors and grow the traffic. Those niches sites have PRs 3-5, are no older than 5 years old and some only a couple of years old. I've noticed if I don't post at a site for months the traffic does go down considerably. It's all about consistency and quality.
Also, make sure to set up sitemaps at Bing and Google Webmaster tools. If your using a platform like Wordpress than have plugins for mobile device viewing install (WPTouch), and a Google XML Sitemap plugin which will ping Google, Bing, Yahoo and Ask when you update.
It's more than just blogging to get traffic, it's all the underlying parts on how you put your site together and of course the topic.