This post is inspired by the Question Box. (If you have a question, this is a great place to put it.) My anonymous Romanian poster says, "the problem is that the protagonist is a female and I seem to have some difficulties in getting the character's pov. Feels a bit artificial, like maneuvering a puppet. I didn't manage to get 'inside.'"
This question makes me think a little of my friends Mary Robinette Kowal and K Richardson - because Mary is a puppeteer, and K is in theater. While I'm not sure precisely what they would say about this topic, I do think the task of getting into writing a character is a lot like the task of acting one.
I personally feel that I need to know a lot about a character in order to write him or her. The amount of what I need to know isn't precisely measurable, and I'm sure that different people feel they need to know different things about their characters. However, I would say that you need to delve deep into a character in order to make him or her feel non-mechanical. What we don't want is for the character to feel author-directed.
So what makes a character feel author-directed? Usually in my experience it's that the character is put into the story for a reason decided by the author, and the author has a lot of ideas about what the character then "has to do" in order to make the story work.
In order for a character to feel organic, that person needs to be self-directed. That means the author should sit down and figure out what that character's cultural viewpoint and backstory is, to the extent that it is relevant to his or her decisions about the actions he or she must take in the plot. The things that we know about our characters show in everything we write about them. If we don't fill them out sufficiently, our own minds and motivations will fill in those subconscious blanks, and that's when the character will start feeling strange.
Here's an example. The character Rulii, in Cold Words, must have difficulty communicating with the human linguist Parker and the human diplomat Hada - but he must not be able to figure out precisely why. In order for this to appear natural, I have to get deeply in touch with the possible factors that may be confusing him. He knows he feels discomfort with Parker when he speaks because Parker is trying to be deferential to him, and he's trying to be deferential to Parker at the same time. That's the surface level. His discomfort is deeper, though, because mutual deference is perceived in his society as a sign of low class, or of extreme intimacy. Because he values Parker, he doesn't want to think of their language as low class, but because he is a Council member in a business relationship with an alien, the idea of intimacy with him makes Rulii very uncomfortable. Furthermore, Parker tries to use an alien term ("friend") to describe their relationship, and the social implications of this are also very troubling to Rulii. When all of these factors come together, Rulii feels very uncomfortable, but enough possible causal factors are present that he can be plausibly confused about which one is the most important.
This is a complex example. However, I'd say to go about creating building blocks for your character's self-animation, you should start simple and let additional complexities suggest themselves (I "discovered" the whole problem with "friend", for example).
Start by considering what you want the character to achieve, and ask yourself whether that is what the character wants to achieve. If it isn't, ask yourself what the character really is trying to achieve, and make sure you have your plot events lined up to push him or her off-course just enough to arrive where you want. Once you know what your character is trying to achieve, ask yourself why.
The harder your character must work to achieve this goal, the more motivations he or she will need in order to justify all that effort. So just wanting to stay alive will work, but it's more powerful if there are also additional personal reasons. Think about what those might be, and try to ground them in something inside the character: a personal motto perhaps, the culture of a group that he or she belongs to, a personal experience with a mentor or during childhood, etc.
I have had the experience of writing a character and having them not do what I wanted them to do. Maybe I'm lucky because my characters do take on lives of their own. But if they're not behaving appropriately, I still have a problem. The moment I try to make them do what I want, they're working for me and not for themselves - they turn into puppets, or bodies, that I have to shove through the motions. Not good.
I know two solutions to a problem like this. One is the one that my friend Janice Hardy often follows: just let the character go where he or she wants to go, and let the story follow. I have a tougher time with this, so I usually go with the second solution: go back and change the nature of the character. If the character is too aggressive, go back and create a background or set of experiences that will temper the character's judgment in the situation you want. Maybe he's aggressive with other men, but his father taught him to protect women and that tempers him in the scene where he needs to be gentler with a female character, for example.
I don't usually interview my characters, but I know many writers who do - or who write a piece from the character's point of view just to let him or her act naturally for a while and help the author feel in touch. That can be a useful piece of preparation, even if you don't actually plan to write the character in first person point of view. I also have a set of questions related to characters and their relationship to the world they grew up in that might be useful, here.
I hope that has shed some light on the topic; I welcome any further comments or questions.