The Protagonist
The Protagonist is the hero of the story! It is their story, and they are the stars of the show.
First and foremost, don’t base your Protagonist on yourself or someone you know. Read Susan Perabo’s article here for more information on why this can be a mistake.
The overall story arc is the vehicle that takes the Protagonist on their journey of growth, and almost everything else revolves around this. So much so, that an individual scene can become irrelevant without it being in the context of how it relates to the character's situation. With this in mind, it is essential that you flesh out the Protagonist’s profile as much as possible.
Qualities readers tend to like in a Protagonist are: dependable, modest and humorous (amongst other things) – read this article by Novel Writing Help for more information on what makes an interesting and likeable Protagonist.
The Antagonist
Every great story features a challenging opponent! There is no easy path for your main character to get what they want and they must encounter an Antagonist who is trying to stop them from reaching their goal.
Several Antagonists may emerge throughout the story, varying in their degree of resistance, however; there should be one clear, major rival throughout the story.
The Antagonist and Protagonist are always competing for the same thing. That is why they continue to clash throughout the story. Antagonists can come in the form of a spouse, parent, police officer, murderer, boss, or just someone who wants the same thing as they do but is determined to get there first.
Make the Protagonist and the Antagonist inseparable. This way one of them can’t just simply walk away. If the Antagonist is the boss or the mother-in-law, for example, the Protagonist will find the situation far more complicated to deal with.
When completing the Antagonist’s character profile, remember that like everyone, they are layered and complex beings. They are not simply ‘bad’. Give them at least some endearing qualities so your readers can relate to them, and even understand their motives.