As previously mentioned, make sure you have prepared two animated characters. One of them should be a humanoid and the other a non-humanoid, a quadruped for instance. You can also download the provided example Unity project and go to the Chapter 01 Working with animationsRecipe 02 Configuring generic and humanoid rigsRigs directory.

You will find there three FBX files: 

• Generic.fbx
• Humanoid.fbx
• Quadruped.fbx

If you are creating your characters from scratch, the bones hierarchy of your humanoid rig is important for Unity to recognize the rig as a humanoid. It should follow this pattern:

HIPS -> SPINE -> CHEST -> NECK -> HEAD 
HEAD -> EYE (for left and right eyes) 
HEAD -> JAW 
HIPS -> UPPER LEG -> LOWER LEG -> FOOT -> TOES (for left and right legs) 
CHEST -> SHOULDER -> ARM -> FOREARM -> HAND (for left and right hands) 
HAND -> PROXIMAL -> INTERMEDIATE -> DISTAL (for five fingers in left and right hands) 

The hip bone is the root bone of the humanoid character. Fingers, shoulders, chest, neck, eyes, jaw, and toes are optional bones. Your humanoid character will work without them.

You should also remember to model the character in a T-POSE. It should face the Z axis in Unity (if your 3D software uses different axis alignment from Unity's like Blender, remember about the -90 and +90 degrees rotation trick shown in the Importing skeletal animations recipe). Hands of the character should be flat, palm down, and parallel to the ground along the X axis. A-POSE characters will also work.