Heroes. Heroines. Sidekicks. Villains. Masterminds. Characters, in general, are important. So, let's focus on them.
Most often or not, the hero of a story almost always has one or more of the following characteristics: Strong, Clever, Reliable, Loyal, Quick, Witty, Charming, Skilled, a Fighter, Love-able, Romantic, Haunted (by a dark past), Hopeful (for a better future), Magical, Courageous, etc.
The hero is the focus of the story and, mostly, the POV. He knows what he wants and will seek it out, whether it is the noble cause of rescuing a damsel in distress, or saving the world. He is determined to see his fate through to the end and protect those that he loves. Of course, he could be the tormented hero, constantly second-guessing and always judging himself. He always puts himself down and demeans himself to the point where he is anguished and lacking in motivation to continue. Usually, this type of hero will have a sidekick or a lovely heroine to keep him in check.
Characteristics of Heroines are usually: Strong-willed, Meek, Crafty, Clever, Wise, Slow-to-anger, Understanding, Caring, Kind, Cute, Beautiful, Intelligent, Tortured, Distressed, Magical, Hopeful, Prepared, etc.
The heroine is the focus of her own story and her own POV. She is dauntless and stubborn when it comes to her task and tries not to stray on her journey. She may be willing to help out fellow maidens (probably more than she would like to help men, especially if she is the tortured-type, ie., she was oppressed by a loved one, or harmed, etc.). Depending on the story, her love interest can always include a hero, a sidekick, and on occassion, the villain.
Characters who will keep the heroes and/or heroines motivated and focused on their cause. They will show their strength only when the hero/heroine needs them most and otherwise will be shadowed by the M.C. until their purpose is called upon again. They are great movers, tending to the plot and making sure that it is seen through to completion, despite the efforts of the villain.
Characteristics will include: Noble, Loyal, Dependable, Smart, Cunning, Silver-tongued, Quick-witted, Ready, Comical, etc.
Usually, these two characters will go hand in hand, if not the same character. They are the darkness that plagues the heroes and the heroines and often find pleasure in the suffering of others. Villains/Masterminds are written to be hated and end up loved just as much as the other characters. Of course, that depends exactly how the author wrote them into the story, because there are some villains that can't be liked.
Often sterotypicalized, just as the other three listed above, the Villain/Mastermind can often be found with the following characteristics: Sly, Brilliant, Dark, Tortured, Deviant, Apathetic, Cruel, Miserable, Foul, Detestable, Harsh, etc.