How would you choose between two characteristics to be used for developing a hierarchy in classification?

The most fundamental and obvious characteristic is taken into account first when categorising an organism in a hierarchical manner. Therefore, the most fundamental traits are taken into account when classifying an organism into a specific hierarchy. Following the first classification of organisms based on a single fundamental trait, additional fundamental characteristics can be taken into account to further categorise them into a certain niche.
The complexity of cell structure, the organisation of the body, and the form of nutrition are the common classification criteria.