Hi,
I found it helpful to doodle using rough circles instead of
thinking too much about perspective. I also found it helpful to make
iterations on doodles each time working as loose and relaxed as
possible. Things like building windows I found it helpful to draw not
by doodling each one but by sketching windows in patterns.
Hope these doodles I made are helpful.
These three show some ideas i felt comfortable doodling with. For some I didn't start with perspective. Some perspective lines in fact began to appear with more doodle sketches kind-of automatically.
cheers,
Nate