1. Enable the “auto tile size addon”. This will automatically optimise the size of your render tiles for best possible performance.
2. Set the Light Sampling Threshold in the render settings (under the sampling settings) to something other than zero. The greater you make this number, the faster the render (but with some sacrificed quality, especially in the darker shadow areas of the image). Here’s what the Blender manual says about that setting:
Probabilistically terminates light samples when the light contribution is below this threshold (more noise but faster rendering). Zero disables the test and never ignores lights. This is useful because in large scenes with many light sources, some might only contribute a small amount to the final image, and increase render times. Using this setting can decrease the render times needed to calculate the rays which in the end have very little affect on the image.
3. Use GPU rendering. This one is probably a no-brainer these days, but in case you are not familiar with the fact, using the graphics processing unit instead of the central processing unit can greatly speed up your renders. Set it in the preferences –> system –> cycles compute device to your graphics card (which hopefully has Cuda support) and the switch to GPU rendering in at the top of the render settings.
4. Use denoising and drop your sample amounts. The new denoiser let’s you get clean images even with lower sample amounts. Simply turn it on in the “render layer” settings and let it work it’s magic.
5. Use the “simplify” option in the scene settings. Just check the “simplify” checkbox and set the “AO bounces” and “AO bounces render” to 2.