Finding supportive running socks that will move with you, wick sweat away, and not cause your feet to chafe are key. After all, you are running 13.1 miles! I love these Nike Elite No-Show Running Socks ($18) because they are thin enough to fit into my shoe comfortably, but provide enough cushion and support. My feet don't slip and slide around, and the tab in the back is big enough that I don't get any chafing.