For the nicer areas of my cities, I try to make most of each city block residential, then designate two or three tiles for 1x1 commercial. Within four or five blocks of each residential/commercial block is a block or two of high-tech industry. This way, the commute time stays very low (I've sustained 30min commute times in cities in upwards of 300,000 res. population). I could possibly make the commute times less, but that would mean mixing dirty industry with my residential, which is something I stay away from. Then, of course, I designate a central location for a downtown core, if I'm building individual cities. For some reason, all of this also helps create heavy traffic in the downtown area, which promotes commercial growth, and creates skyscrapers. Then, sprawl it.
