The zones are jsut what I got when i clicked and held to make them... I like to look it at as the sims that live there telling me exactly what they want in a house or place of business...
My thinking for placing all of the services at the beginning is that I had all these small empty spaces in the city and I figured if I covered all the bases right from the start I wouldn't need to worry about adding in many municipal strucures later on... I am still getting stuck with having to place the High School College and University jsut so I can begin to get any real nice types of development (HT CO$$$)
Also when should I add some new zones , of what type, and where? I have ran with the city not adding any new zones, it fillls with nice large mansions but they all become dilapidated evantually...