Once you're happy with the roads in your city, start placing the medium buildings. Players get 10 points for smashing these, so try to place the same amount of them near each SpawnLocation.
Duplicate and move the medium buildings onto the map.
Place 8 - 10 medium buildings, adding more roads as needed.
Next, start placing provided props, such as trees or cars, around the map. Players don't get any points for smashing these; they're there to add realism to your world.
An example of props placed is below.
Note that some props, like cars might not snap as you desire. For unrestricted movement, you can turn off snapping by going to the Model tab and unchecking the box next to Move. If you've finished moving props, be sure to turn snap back on.