Brandy Colbert is the author of POINTE, winner of the 2014 Cybils Award for young adult fiction, and was named book of 2014 by Publishers Weekly. Her next book LITTLE & LION will be published by Little, Brown in spring 2017.
POINTE was the fourth novel Brandy wrote. She knew it was almost there because she really started caring about the characters.
It really helps to create a backstory for your supporting characters, though you don't need as much as you have for your main character, but they too need a story. Be careful of stereotype with your supporting characters.
Watching TV is a great way to learn about great dialogue. While watching it's helpful to assess what people do with their hands and body language. Also, close your eyes and listen to what their voice alone sounds like.
Do your characters use certain words or slang (but also be careful of these)?
Empathy is huge. Give readers a reason to care about your characters.
What Brandy worked on most when writing POINTE: detail, detail, detail, and body language. She wanted to allow the reader to imagine the characters as much as possible without giving to much detail, but Brandy's editor was often asking: Where is she? and Where are you characters on the page? She had to work on this.
Supporting characters Brandy loves (from contemporary, realistic):
The Best Friend
A Sense of the Infinite by Hilary T. Smith
Roomies by Sara Zarr and Tara Altebrando
Nothing Like You by Lauren Strasnick
P.S. Be Eleven by Rita Williams-Garcia
Making Pretty by Corey Ann Haydu
The Walls Around Us by Nova Ren Suma
This Is Not a Test by Courtney Summers
Characters That Don't Appear on the Page
Hold Still by Nina LaCour
Since You Asked by Maurene Goo