I guess this is more of a general 3D question than specifically of Blender.
How can I separate my scene in layers to render my animation faster on Cycles? Meaning, is there any rule what should be on what layer and how should it be composited? I don't want to spend a huge amount of time rendering the whole set for each frame when I can just render the animation and composite it over the BG.
There's a lot of tutorials on how to do it with stills, but I haven't been able to find anything regarding animation.
Thanks a lot!