Characters are the soul of your novel
This is why you need to make them memorable. The authors of this novel have done research so you don't have to. This book includes dialogue(what not to do and how to make the characters distinguishable), how to do background stories (what draws readers in and what makes them turn the pages), physical appearance (not everyone should look the same, adding diversity makes your story believable)...and so much more.
If you enjoyed this book check out:
Query Perfection: Your Guide to Query Perfection: http://www.amazon.com/dp/B00IVT71DQ