If you havent see it already, check out the links in shor's comment below - there are some great resources in there. In some cases you can also consider surveying your current audience or customers through email, on-site surveys or SurveyMonkey. Be sure to ask for some profiling information that you can use for determining specific persona needs like age, sex, location, etc. (Probably best not to make it sound like a creepy text chat like I just did though...) :)
Google Analytics is an invaluable source of data on just about every conceivable aspect of your site, from your most popular pages to visitor demographics. Keep a close eye on your Analytics data, and use this information to inform your promotional and content strategies. Pay attention to what posts and pages are proving the most popular. Inspect visitor data to see how, where and when your site traffic is coming from.
Another way to increase traffic to your website is to get listed in free online directories and review sites. For most of these sites, your profile will have a link to your website, so actively updating these listings and getting positive reviews is likely to result in more website traffic. In addition, many directories like Yelp have strong domain authority on Google. There’s a chance that your business’s free Yelp page could rank high for relevant searches.