Important options to note are the Frequency and Shading Quality. Shading quality will have a big effect on the render time, so you should reduce this to only the minimum needed. Frequency will essentially create larger or smaller clouds. It's recommended to play around with each of these settings and see in the viewport exactly what differences they make. It's possible to make some very realistic and interesting clouds, mist, fog, and smoke using this container, and it's also very easy to animate, so make sure it's one of the tools in your arsenal.
Note on the right side under Render Stats, I have unticked Receive and Cast Shadows. There is really no need for this with mist. You can also uncheck Primary Visibility whilst tuning the rest of the scene, turning it on at the end when we want our mist to show (Fig.19).
Now duplicate this fluid by copy and pasting and then move it to cover the area under the left window and in front of the camera. That should fill up that area nicely and we can move on to creating our depth fog.
Create a new fluid container that fills up the location from the camera to the steps, and also fills the whole area up vertically. Use the same settings as the mist for Display and Contents Method. Turn off Texture Color and Texture Opacity, under the Texture dropdown, as all we need is a fine fog.
As you can see it is very easy to create depth fog in the Maya software renderer, however, that's unfortunately not the case with Mental Ray (Fig.20).
Under the Shading dropdown, we need to increase the Transparency to 0.999. It should be really fine and see-through, but noticeable in the render. The dropoff can be set to Cube and Edge dropoff set to around 0.8 to ensure it's not obvious when it touches the buildings (Fig.21).
Now that the scene is starting to look respectable, we need to add some elements to make it a bit more interesting. We can start off by turning on some of the lights in the windows, namely the one above the door and the one on the right hand side, seeing as those will be primary focus points in the image.
In your image editing program, select the panes of the window on the texture and either use Hue Saturation and Lightness to turn them into a bright yellow, or you can simply paint them yourself. I find painting the edges of the glass darker helps sell the "light on" look (Fig.22).