Sorry, this isn't a pep talk. It's about writing. We all have different types of motivation and we all need it. It's what moves us and makes us act--or not act. And like conflict (see my post on types of conflict here), it's universal to all genres of writing. Humans need motivation and so should characters.
Every single character in your books, from the main character to the love interest to the janitor who is only in one scene, should have a reason behind the choices they make. Bad guys and bullies don't behave in an obstructive manner simply because they are "evil." They too have a motivation and a justification behind their actions, though it may be a twisted one.
And most characters don't act under a single driving factor. Katniss for example wanted to protect her sister, give them a better life while also wanting to escape it, desired to spend time with Gale, kept a wary eye on her mother, had a thing against the elites like Peeta, and probably deep down had a desire for revolution, all wrapped in a drive to survive and the wish to hold it all together for her dad.
The choices we make aren't determined by one desire. We're a roiling mass of conflicting emotions and worries and drives. The best characters reflect that. They have more than one factor pushing at them. More than one thought in their head.
Take this post for instance. I wanted to share a little of my experience with others who may be just beginning, but I also wanted to clarify my own ideas of motivation to myself. I needed to fill spots in my blog or it would sit empty, and it would be a nice bonus if it brought attention to me and sold some books--because people gotta make a living. I also needed a break from working on my WIP. Multiple motivations. And there are probably deeper ones buried having to do with ego.
So if your character has just one dream, say to get into an Ivy league college, they are probably going to feel a little flat to the reader. There should be a whole messy swirl of desires in their head and heart, probably conflicting at some point.
Ramiro from Grudging started out wanting very much to be like his brother and take his place in the military. Personal honor is a big part of his personality. Being reliable and dependable. Proving himself to his brother and not being an embarrassment. Thinking and not simply reacting during battle. Then there's his desire to keep his horse safe and survive the day. And deep down a desire to be his own man and not like everyone else. And of course those are his motivations for just the first chapter.
Like life, your desires change as your situation changes. Motivations aren't going to stay consistent over the life of a story. They'll evolve as a character evolves.
Recently I started reading a story rather like Cinderella, only this story failed to provide any motivation. In Cinderella, the stepsisters and stepmother had reasons behind their treatment of Cinderella--fear and jealousy. Fear she could take everything away from them. Fear the dad would like her better. Jealousy that she'd get what they deserved.
This story had a parent and siblings picking on the youngest member of the family. The older siblings got all the good treatment, were trained for society. The young main character had to sleep in the dirt, got teased and bullied. But immediately I'm thrown out of the story because they had absolutely no reason to act this way. All the rest of the family got along fine, why arbitrarily pick on the youngest? The MC wasn't deformed or simple minded or different in any way. There was simply no motivation for their crusade against him and it ruined the story for me. Maybe a motivation will appear down the road--maybe the MC isn't really related to them--but it's probably too late. I'm likely to quit reading before that happens.
So what should you do when you can't reveal the motivation of a character? Besides dropping a few hints, the author of that story could have had the MC be just as confused at their treatment as the reader. If the MC dwelt on the randomness of it, I would probably have let it go--accepted that and moved on--instead of letting it spoil the opening chapters.
As you are writing and editing keep in mind that characters need reasons for what they do and how they react. A character without a motivation is a hollow shell.
If anyone finds this, I'll give you a copy of Grudging. Just let me know.