Habits and mannerisms must originate somewhere, for some reason. In a novel, where aspect of a character should be intentional, a character’s mannerisms should do more than differentiate them from the rest of the cast but should enhance their unique personality.
In her book Getting Into Character, Brandilyn Collins suggests that a character’s mannerisms should evolve from an understanding of the character’s core values. Those values lead to the character’s motivations, and those motivations are shown through specific mannerisms.
For example, a character in my novel is a retired centurion. Like many Roman men, his primary core value is honor. He believes honor comes from fulfilling his duty in a responsible manner, showing courage in the face of danger and always considering the consequences of his actions. He sacrifices self-gratification for what he believes to be the higher good, which leads him to disapprove of the trappings of luxury, which in turn leads to his habit of pinching pennies. (Much to his socialite niece’s frustration.)
During his service in the legions he learned to keep his face impassive no matter how much turmoil or doubt he felt. This forced control over his emotions has become a habit, but it comes at a cost, and he often rubs his temples to ease the stress, especially when he feels his control slipping. Thus the mannerism of rubbing his temples is not merely chosen at random, but evolves from his need to maintain honor.
Another character is a self-centered, wealthy widow whose deepest need is to be in control of her own destiny—a difficult thing in her male-dominated world. Rather than choose the route of open rebellion, she opts to stay within the bounds of society, but does whatever she can to manipulate people and situations to suit her ends. To her image is very important. If she appears confident and in control at all times, others will naturally bend to her will. Therefore, she never leaves her room unless she is completely put together: hair, jewelry, cosmetics and fashionable clothing. Not only does this radiate confidence, but it gives her a sense of control over her physical image. (If she were a modern woman, she would take full advantage of techniques like botox.) Another of her habits is that she takes five deep breaths before facing a strong male, to get her emotions under control and steel her nerves, because she cannot allow anyone to perceive her as weak.
