To help you learn the first principles of a human’s growth and development, I recommend this book:
Developmental Profiles: Pre-Birth Through Adolescence https://www.amazon.com/dp/1111830959/ref=cm_sw_r_cp_api_i_Z-4FFb9D9T7KH
It will tell you what to expect and the milestones they need to hit and when. It talks about all areas of development from infancy to ~18 years. Knowing the underlying theory might help- it did for me! Best of luck!
http://www.amazon.com/Developmental-Profiles-Pre-Birth-Through-Adolescence/dp/1111830959
What about this? Is this something you are familiar with, or do you think it would be worth perusing?