You Really have to find that out your self. for me i looked at others and copied and made random tweaks and then eventually found out What colors material (etc.) that I preferred to use and that lead me to what I draw now
It's hard to explain but it's different for everyone so yea
Answer:
It is the best way for potential employees to demonstrate their skill.
Explanation:
It gives the company the opportunity to see what you are capable of and if they would want you to work with them based on your skills and creativity.