See Pattern Language/Christopher Alexander for ideas on how to design the physical spaces to work for the people who will be using them, including random passersby.
Put cars lowest on the priority list. To me it feels like you should only need a car to travel between neighborhoods, though there would need to be a solution for elderly/less mobile folks.
Build the city near some beautiful nature, and then put a free public transit line that gets people from the city center to there, fast. I live about a 10 minute drive/30 minute bike ride from a beautiful national park, but I rarely go there because it's not fast and easy to get there.
Subsidize a good amount of small office/storefront space for new businesses. Let people try out ideas for shops and businesses without going into crazy debt just to sign a lease.
Make efficiency/sustainability requirements for building WAY higher than the norm. In many climates, AC/heating isn't actually needed if you invest a bit more in building materials upfront and build intelligently.