How to decrease rendering time???

How can I reduce rendering time speacially for animation???

Not much information, best is an example file.
But, not a hell of a lot lamps, lowpoly as possible, fake objects with planes, change render acceleration structure, set more threads.
You could use a renderfarm like renderfarm.fi.

Cheers and welcome, mib.

check this article: http://renderflow.blogspot.com.es/2012/03/tutorial-blender-referenciar-personajes.html - it explains how you can reference characters in your animation scene from scene libraries - makes your scene lighter

Use a faster computer. Render to a smaller size. Don’t use reflections at all. Turn off shadows.

Moved from “Basics & Interface” to “Lighting and Rendering”

Basically, you have to simplify the problem for the computer. Make it computationally require less work. Choose a workflow that relies completely upon compositing, so that you can independently prepare different components, or aspects, of the shot one-at-a-time, and so that you can change aspects of the shot without completely re-doing it.

You can be looking at the shot in actual context, after it and surrounding shots are “finished,” and, yeah, maybe come away with the feeling, “y’know, this really isn’t quite working for me.” (It happens.) You can at that time articulate what you need to “add to the mix” to correct the issue in-situ.

In the case of animation, shot by shot, you want to have enough to properly carry the shot, but not one whit more. If a close-up shot is followed by a long shot, the eye will actually see what it expects. It is an established fact that, during the first theatrical release of Star Wars Episode One, a briefly-seen crowd in a podracer sequence was actually a collection of colored Q-Tips cotton swabs. No one noticed, including me, until the trick was pointed out in a “Making Of” video. (The shot has since been replaced.)

Once the viewer’s eye is focused on the acting and the story, your shots simply need to be “enough.” And, to quote Michael Douglas’ character in “A Chorus Line”: “don’t draw my eye.”

You do need to pay very close attention to consistency. Look at a series of related shots in the chroma-scope. Pull a histogram. Establish early on the materials and textures, the color and intensity and position of the lights, final color-temperatures and so on. So-called “color grading” can resolve inconsistencies late in the game but early consideration of it will make your life easier.

All of these things do “decrease rendering time,” not only because they make the problem simpler for the computer, but also because they sharply reduce the probability that your previous efforts will be scrap.