We need to stop building bad places. We don't need to build Rome or Paris. We just need to stop building Houston.
The following eight rules apply to every major and mid-sized city with no exceptions. If your leaders don't do these, somebody else's will. And, you'll have people asking in 10 years time why you haven't already done them.
1. Make accessory dwelling units legal
This is the easiest way to add density without adding "density". This won't change your city overnight, but it'll help lay the groundwork for improved urbanism. We need to see a rise in these types of dwellings because they add to affordable housing stock, expand housing options, add tax revenue, and are Jane Jacob's "eyes on the street". Except in this case, it's eyes on the alleyway. Read more about accessory dwelling units here.
2. Eliminate parking minimums as soon as possible
There is no bigger detriment to urban centers than parking. It adds costs to private development and drives up rents. Car storage is a terribly inefficient way to allocate land, especially in existing walkable neighborhoods. If you want to make your downtown more livable, the first policy move should be to eliminate (or, reduce if elimination is not politically feasible) all parking requirements.
If you worry about parking (and "congestion"), you might lose great local institutions to the suburbs. I'm looking at you, St. Paul.
3. Four-three conversions of stroads