I love running (as in jogging) stores. I love to run so I could spend all day in a good running store, gazing all the new accessories, trying on new shoes, chatting with other runners, etc. I'm sure the owner of my local running store would love to be able to market to me even when I'm not in the store. They could do just that with a blog for their running store. But when they get back from their run, what should they blog about? Well that's easier than a 30-minute 5K, which is to say it's doable but it takes consistent effort, quality planning and a whole lot of stick-to-it-ness.
The most obvious thing to blog about is, well, running. No, not "Running good; Sitting bad." I'm talking about something like "Four mile group run next Thursday, everyone's invited!" Make your store the gathering place for your particular niche. A half-dozen or more runners showing up at your store every Thursday at 5:30pm is a thing of beauty. Get connected with those folks and keep them connected via your blog.
Training, races and other events should also be seriously considered using the ideas mentioned above. Take your products out of the picture and make your place THE place for local runners to be involved and you'll on your way to a business PR (Personal Record, for you walkers out there).
How about offering your blog readers exclusive in-store sales and promo items? You could post a 3-day promo for all men's size 9.5 New Balance shoes, for example. Get the stuff in your store directly into the hands of the right customers by giving your blog readers fast, easy, organized access to what you've got. Of course, keep the meat of the content about local running issues, races, news and tips to ensure your blog has continued value to its repeat visitors (your most important blog visitor).
Couch potatoes, there is hope for you! Strap on a pair of sneakers and...oh no, I mean, start making your blog the gathering place for local customers. Fill your niche entirely. Draw people in through your blog, give them reasons to show up at your door and offer them as-customized-as-possible information quickly and easily. It'll make you a star on or off the track.