When writing a story, you always have to keep in mind 3 things: characters, the plot, and motives. Really, everything about your story is important, but when it comes down to actually making a work that people will want to read, the readers will enjoy seeing these three elements at their best. Characters are what connects your story to real life and makes it more touchable, less of a stranger to your reader. Plot is, well, what your story is about. And motives are the things that often writers (myself very much included) forget to think about. Motives aren't so much for the reader to notice, but without motives the story will be meaningless.
Motives are really important not only because they give meanings to actions but because of the characters you can create when you put motives conflicting with actions. A villain might want to destroy an entire city and all of its inhabitants, but maybe that's because the teacher in that school down the street throws his garbage into the villain's lawn each day. If the motives are good and understandable, but the actions are seemingly dreadful, the villain is perhaps more likable or loathsome. Either way, that villain isn't just an angry old lady shaking a cane, they have become important. Your villain needs to be destroying something or doing something bad because they want to and enjoy doing it, or else they would have been defeated a long time ago and really shouldn't exist.
You can actually change a whole story just by changing the motives. If Cinderella wanted to marry the prince to be rich as opposed to because she was in love with him, we would have a very different opinion of the whole story. The step-sister's motives to make fun of Cinderella are mean along with their actions, so we automatically form a bad opinion of them.
Developing a good character is very important, however. If your character isn't very well defined, and you throw in some details about motives and actions and how they conflict with each other, you will confuse everyone, including yourself.
Another thing: don't make your story too complex. Just because there should be underlying emotions, motives, and character traits does not mean that you should write a whole 5 pages on the internal conflict of so-and-so because it makes the story more complex. Don't feed all the information to your reader in a couple pages. You have to leave room for your readers to create parts of your character. No matter how hard you try to prevent it, every person reading your story will differently interpret your character. But that is never a bad thing. That's what makes stories special!
Do you have any creative ways to portray a villain or other characters? What do you do to make your story more interesting? Share with me your ideas in a comment!