There is no recipe to writing a novel. There are many do’s and don’ts. The thing to remember about writing rules is that you need to learn those rules so that when you break a rule you are fully aware of it.
Whose POV (point of view) do you use for a novel? Whoever has the most to lose! Once you figure that out you have your main character. In a romance you have the hero and the heroine, period. In Women’s Fiction you have more POV’s you can use. Read the type of novel you are going to write and learn from those authors. How many POV’s worked for them?
Make sure that if you use a POV you use it frequently. Editors frown on a new author using a POV two or three times in their novel. Make sure that each POV character has a GMC (Goal Motivation Conflict) chart and that they have character growth. A solid GMC chart makes for a more three dimensional character.