Find an area that you're interested in, blog on it, daily, and then keep doing it for ten years, even when it seems out of fashion, even when it seems like your influence is waning and other people's stars are rising. Reflect your reading, your learning, your developing understanding of the field. Stay true to your own values, and don't relent when it looks like you've peaked.
If I go a week without blogging, that wobbly, nagging feeling I get owes less to an obligation I have to an audience and more to the fact that this is the place where I learn and an outlet for my excitement. If I don't blog for a week, then either a) I haven't learned enough, b) I haven't been excited by enough, or c) I haven't carved out enough time to keep that learning and excitement cycling through my brain. Blogging, in any of those cases, is a nice way to step on the intellectual scale and take a reading.