My historical novel (second of a three-part series) involves a first person narrator/protagonist named Jack Clark, who in 1801 travels to Tripoli at the behest of Thomas Jefferson. There he finds himself caught up in the beginning of America’s first foreign war.
It’s relatively easy to keep Jack’s voice consistent because he’s the character doing most of the talking, either to the reader or to others in the stories. But what about them, those other major and minor characters? How do I keep them consistent, and individual as well?
Putting myself into their heads, is one way to put it. And I do it one character at a time. That is, after I’ve got a first draft — whether it’s just a scene or chapter, or the entire book — I read through for each character, one at character at a time.
During these readings I ask: Does she repeat herself? If so, is that one of her character traits, or is it lazy writing? Does he speak in a consistent manner? If not, is it story context driving the differences, or is it just more lazy writing?
There’s, more of course, but if you find yourself thinking, ‘this character is a different person,’ you’ve discovered something that would distract your readers, even if they weren’t sure why. Armed with that knowledge you can fix the problem, and your narrative will flow better.