I grew up drawing more cities and architecture than I did people, so cityscapes are kind of my natural habitat. Never looked up a tutorial or guide on cities, so I'm sorry I can't offer you any resources there.
I think that as long as the characters seem like they belong in that environment rather than pasted in, it does its job.
Lemme try an example:
This is a cool shot, but the contrast between the hard-outlined character and the painted city does take me out of the story, which is what an establishing shot like this shouldn't do. Outlining the buildings that are closer to "us" would help our character "fit" into his environment.
But it does a great job of establishing tone, which is something an establishing shot should do. (I'm getting late-night gloom with some blues or jazz in the background, like those detective movies.)
Perspective is also something a lot of people would say is important for environmental shots, but I can say it's up to the art style. My art style is big on getting that 3D space across, but I've seen plenty of art styles that forego realism. Like I said at the start, as long as the characters seem like they belong in that space (art-style wise) any city shot works.
I'm adding this portion in an edit because I realize I didn't actually talk about how you can get 3D space across. (In case that's what you came for.) Before starting on a scene, you should decide where the horizon would be, and your space expands outwards from that horizon line. You can use a 3D modelling program or ye old perspective grids for help, but they all lead to the same concept.
In the image above, I notice the windows on the right side of the street not fitting with the building's angle. If you imagine the windows going on forever, the "rows" of windows would approach the horizon line.
wow that is crudely drawn
