I have made only one or two of my lights, cast shadows. If you have many lights producing shadows your render time will also increase loads.

By adding more lights, the scene will become brighter and brighter, so I've assigned my lights to certain objects within the scene, which will then leave my shadow-producing light to illuminate all the objects. I've also disconnected the lights and objects apart by selecting both the light and the object, which I don’t want this light to illuminate, and then click Break Light Links under the If Lighting/Shading menu. Just remember to have the object assigned to a light or it will be just a dark shape without volume

About previewing the final render :

Before proceeding to your final render you will have to test with a single frame. This will show you how much time it takes to render every frame and how your scene really looks.

You can use the Snapshot and Render Region functions in the render view to preview the wireframe and, render only a region of the image.

This is useful because IPR doesn’t support Mentalray and Raytrace. I use IPR mostly to see how the bump looks for my textures

About the Render Settings :

Go to the Render Settings, if you are rendering with Maya Software, go to the Maya Software Tab and set Production Quality and Gaussian Filter Type options in their corresponding field.