If you’re opening a restaurant, don’t blog about your menu. Blog about great food. You’ll attract foodies who don’t care about your restaurant yet.
If you make superior, single-source chocolate, don’t write about that great trip you took to the Dominican Republic to source cocoa beans. That’s all about you. Instead, write the definitive article about making chocolate-covered strawberries. For the next 10 years, whenever a gourmand or a baker searches Google for a recipe on how to make chocolate-covered strawberries, he or she will find your post. Helping your users make awesome chocolate-based confections is likely to attract readers who might buy fancy chocolate, and that’s the point of a successful blog. Writing about trips to the Dominican Republic is going to attract only people who might want to travel to the Dominican Republic. Unless you’re selling that, you shouldn’t be blogging about it.
In retrospect, Joel on Software was essentially a small, perfectly targeted magazine for programmers with a certain pragmatic philosophy toward software development. It was also free advertising for my company, but the advertising actually looked a lot more like editorial content than anything else; the most popular post I ever wrote, for example, was about how technology companies should never, ever rewrite their code from scratch.