Keeping rendering in mind when you model a scene can help you reduce rendering time. For more information about modeling, see Modeling and Deformation Basics.
Try to reduce the number of objects in each scene. Using fewer objects keeps the rendering time down.
Try to use the lowest number of polygons possible on polygon meshes.
Try to reduce the complexity of NURBS objects. Often, you can use surface approximation to make them look smooth at render time.
Use subdivision surfaces (subdees) to simplify the model and the texturing process.
The more geometric detail an object has, the longer it takes to render. Try to substitute some of an object's geometric detail with a texture map. From a distance, the difference may not be distinguishable.
You can simplify the calculations required for shadows, reflections, and refractions by adding invisible objects to the scene.
Suppose you have an object that is generally spherical but has a great deal of surface detail. Set its object properties so that it is visible to primary rays and secondary rays but does not cast a shadow. In the same position, add a second, simpler object that casts a shadow, but is otherwise invisible.
The end result is an image that appears correct but for which the shadow computations are much less expensive. A similar technique can be employed so that secondary (reflected and refracted) rays see a much simpler object.
Adjusting an Object's Surface Approximation
Depending on your method of surface approximation, you can reduce the number of triangles in an object, but still obtain a quality render. Reducing triangles decreases the amount of time necessary to transmit the information required to render a frame across a network and it also decreases the amount of memory and swap space required to hold that information. See Applying and Editing Geometry Approximation [Scene Elements].