Powerful story-telling requires identifiable characters. The reader needs to relate to the experiences and/or reactions of the protagonist(s), and they need to find themselves repelled by the antagonist(s). For an author this can be tricky, but I think one key to identifiable characters is focusing on the character's life experiences.
You could say that I place a lot of emphasis on history; in this case, fictional history; those background details which provide character motivation and enhance the story-world. In life, our experiences shape us. But, depending on our reaction to them, they can improve, strengthen, weaken, mold us. Or, if we are a steady individual of pure logic, such as Spock, our experiences will leave an impression but change us little.
In my recently-released novel, The Sword of the Dragon: Offspring, I had a lot of fun with the characters. In particular, I enjoyed Caritha, Rose'el, Specter, and Ilfedo. I have come to know those characters better and thus their stories are proving easier to tell. Again, characterization, the best kind, is all about history!
The sketch above was original artwork by Amber Hill for Offspring. It beautifully conveys the friendship of Oganna and Vectra (who you'll read about in Offspring)!