First, spatial imagination, roughly understand the relative relationship between points, lines and surfaces;

The second is planarization, which means that some elements that need to be solved can always be solved on a plane (including constructing auxiliary points, lines, surfaces, etc.). );

Third, we can solve problems by understanding common models. Such as tetrahedron, cube and transformation (such as cutting off an angle) and so on. This method is intuitive and easy to understand, and it is often effective and convenient to solve problems.