Hey there, folks!
Today I'll teach you what the "Rule of Thirds" is and how to use it in Blender.
The Rule of Thirds is a basic composition guideline which helps you composing your image / placing your camera. This guideline is very often used in photography, painting, and 3D art of course.
To use the rule of thirds, we have to divide the image / our render by two equally spaced horizontal lines and two equally spaced vertical lines, resulting in four intersections. We place our most important object in the scene or the thing we want the viewer to look on at one of those intersections. (Watch the image above to understand it better.)
In Blender, we can do this in three easy steps:
1. Enter the camera view by pressing "0" on the Numpad and right-click on the camera border to select it.
2. In the properties panel, go to the camera tab. You'll find a section called display, and a drop-down menu called Composition Guides.
3. Choose Thirds from the drop-down menu (I rarely use any options other than thirds, but the Center Diagonal can be useful sometimes) and you'll get a handy rule of thirds overlay.
As you see on the image below, I arranged the camera so that the objects I want the viewer to look at first - in my case, it's the front of the table with some chairs - are placed on one of the four intersections. The objects don't need to be super perfectly aligned, but the overlay really helps to place the camera in 3d space.
Additionally, you can increase the Alpha, so everything out of the camera is darker, which gives you clearer look on your composition.