#1 - Target Your Content to an Audience Likely to Share
When strategizing about who you're writing for, consider that audience's ability to help spread the word. Some readers will naturally be more or less active in evangelizing the work you do, but particular communities, topics, writing styles and content types regularly play better than others on the web. For example, great infographics that strike a chord ( like this one), beautiful videos that tell a story (like this one) and remarkable collections of facts that challenge common assumptions (like this one) are all targeted at audiences likely to share (geeks with facial hair, those interested in weight loss and those with political thoughts about macroeconomics respectively).
If you can identify groups that have high concentrations of the blue and orange circles in the diagram above, you dramatically improve the chances of reaching larger audiences and growing your traffic numbers. Targeting blog content at less-share-likely groups may not be a terrible decision (particularly if that's where you passion or your target audience lies), but it will decrease the propensity for your blog's work to spread like wildfire across the web.
#2 - Participate in the Communities Where Your Audience Already Gathers
Advertisers on Madison Avenue have spent billions researching and determining where consumers with various characteristics gather and what they spend their time doing so they can better target their messages. They do it because reaching a group of 65+ year old women with commercials for extreme sports equipment is known to be a waste of money, while reaching an 18-30 year old male demographic that attends rock-climbing gyms is likely to have a much higher ROI.