I think Urban Design must be think about following principals,

1, Think about land use. Analysis of Urban Development and the entire design. Rational use of land .

2, think about surrounding buildings and even neighboor towns. Attract more people from the town next to the site, and make it vibrant and works.

3, traffic! traffic is the most important thing to think about. No traffic no future.

4, Promoting economic and social development, think about the future.

5, think about environmental and save land.