Characterizing Secondary and Minor Characters
Now that you realize what goes into fleshing out your protagonists — goals, flaws, careers, hobbies, and secrets — you might be wondering if you really need to give your secondary characters the same attention.
The answer is yes.
Every character appearing in your novel needs to come across as real to the reader, no matter how small a part he or she plays. The more vivid your writing, the more a reader loses herself in your story.
Just because the character isn't your main protagonist doesn't mean they should be a cardboard character. Secondary characters who play a role in the novel need depth, goals, and layers of interest. But how many of those layers you pull back and expose for the reader will depend on the character's importance and how those layers of interest will play to the novel's main theme and plot. If you go into that character's point of view in the novel, then the reader will automatically expect to see more of the character's internal makeup.
Every character introduced into your romance novel should serve as a mirror to reflect your main protagonists. By using the technique of compare and contrast, a good author knows secondary and minor characters are great tools to enhance the characterization of the main characters.
If the character is only on stage a short time, you may not need to paint the entire life story of this person. But this doesn't mean you can't give insight into a character using very few words. Sometimes, quick brushstrokes can not only tell you what a character looks like, but give the reader insight to background, moral compass, and immediate goals. Never add description solely for description's sake, though. Use other characters and their characterization to allow the reader to get a better view of your protagonist. For example:
While the waitress may not appear again in the novel, the author uses the character of the waitress to show insight into the heroine's situation and emotions. How much you choose to expose of your minor characters depends on their importance to the plot and if it will help you create emotion in a scene.