Restrict yourself to a single, focused topic for each of your blogs. If you spread out your blog's topics too much, they will become cluttered. This technique for simplistic writing is easy to implement, and will immediately improve the quality of your content.
Advertising freebies that you give away can generate a lot of traffic to your blog. People love a freebie, so it doesn't need to be a big deal. The more contests and freebies you have, the bigger the payoff for you, in terms of readers and followers. If readers think you might be having a give-away, they will come back to check your blog.