Make render preview faster Is their a way to make a render preview in the viewport shading faster in cycles? I only know about reducing the samples to make it faster.

Of course at the cost of quality whatever it might be,i often find myself noticing problems in my animation too late, after rendering since i can't preview the animation fast enough before rendering...(i tried to make a smaller preview render of a whole aimation before the real render but it does not help me much)
You can use ctrl-b to draw a rendering box, so that you preview doesn't have to draw the whole view.



You can enable Simplify in properties/scene, which will allow you to create separate settings for subdivision for preview, or to create a hard limit on light bounces so that they'll (as in this pic) just skip to AO (white world) after 2 bounces instead of doing more.

And of course, you can do any of the things that you do to keep renders fast.  I avoid shaders I know run slow (volume scatter, glass, SSS) mostly because of their effect on my preview.