Identify the chest voice by strong notes in the lower register. The chest voice is mentally and literally felt in the chest and carries a strong timbre quality. The sound is confident and pronounced.
Distinguish a head voice by the lilting quality of the higher register. The notes will be in the upper middle and upper range and generally have less force and a gentler sound.
Study the mechanics of singing to understand the physical difference between head and chest voice. The chest voice literally resonates in the chest and vocal mask, or face. The head voice moves up into the nasal cavity and the vibration moves up into the forehead. A soft, open back of the throat is associated with a head voice while a bright, forward resonance that vibrates the lips is associated with a chest sound.
Find your break between the chest and head voice by practicing scales. When you feel the vibration move from your chest up into your head that is your break. Train to blend the head and chest voice at the break to decrease the obvious difference that can be heard in most untrained voices.
Look for differences of head and chest voice in popular music. Bing Crosby has a classic head voice quality while an Ethel Merman sound is definitely more chest voice.