Short Version on Characters

On characters, short version

Give them motivation that arrives from backstory.
Give them a secret.
Give them connections with as many of the other characters as possible.

Read jim-butcher.com's blog about writing. It's one of the tabs.
Visit writingexcuses.com.
Take a course on creating characters on line or in person.

Top down or Down up development--the end result is the same. Think of a coloring book--they are boring as hell for an adult. Now, take that and put it into an artist's hands and it turns 3D and beautiful or terrifying or compelling--just maybe all three. You want to make sure that your end result has maximum impact on your reader. You can't end up with your first thoughts and motivations for these characters; they have to be ten steps beyond your first ideas. Strive for depth, but always logical, realistic and often simple characteristics. If your character isn't speaking to your heart, then she will not speak to the reader. If she can't make you cry, the reader won't either.