My commute is just under 3 miles, and I suppose I do plan somewhat. I often ride different bikes to work, so I have to make sure my multi-tool, pump, spare tubes, etc. are on the bike I plan to take. I also usually take my lunch, and I choose which bike to take based on rain, whether I intend to get groceries after work, etc. I don't really wear any special clothes, but if it's raining I take spare clothes and in the winter I wear a rain coat. But other than that I just wear the clothes I work in.