Tips for faster rendering

I thought I'd share a few tips for those who are struggling with long rendering time of the final images.

1. Rendering via CPU or GPU: 
   • If you have a graphics card that supports the option, and you select "GPU Compute" in the 'Render' tab - 'Render' section, you will generally be able to render faster, but only if you also change the tile size.
   • The rule of thumb for tile size is "CPU = small tiles (16x16 or 32x32)" and "GPU = large tiles (256x256 or 512x512)".
   • If you select GPU and small tile size, you are going to have a bad time rendering (it will likely take longer than if you had used CPU).
   • You can change the tile size in 'Render' tab under 'Performance'. I also like to use the "Center" option for the rendering order.
2. Number of samples with Denoising on:
   • By default, the scene is set to render with 2000 samples, which is going to increase the render time significantly.
   • But, if you are using Blender version 2.78.5 or higher, you can use the "Denoising" option found in 'Render layers' tab. You can play with the settings but the default should work just fine.
   • With this option on you can lower the number of samples and you will still get nice result (I used 500 samples for daytime scene and 750 for the nighttime one).