What does your character want? It seems so simple and yet it is so indispensible to story. If you have not determined what your character wants throughout the course of the story – or in a particular scene, for that matter – then they are not going to come across with strong objectives – and therefore create drama. Even if your intention is to create a character who vacillates emotionally, perhaps this is only because what he really WANTS is to be loved and accepted, as this is often one of the ploys humans take to secure love – changing themselves to fit into someone else’s world instead of sticking to what they, as individuals, want.
An actor’s job, of course, is to interpret what a character’s objectives (wants) are. But it is the writer’s job, not the actor’s, to develop those wants in the story. If a writer has not done a good job of doing so, then the actor will not have much to go on.
But the real question is what the character actually NEEDS? The character may want something, which drives him, but at some point he will have to be pushed into figuring out what he needs. It is often good to heighten the stakes by creating a situation in which, if the character does not figure out and DO what he needs to do, instead of what he just wants, then bad things are going to happen (e.g., he is going to lose someone he loves or maybe even die). The act of the character figuring out what he needs to do is what lies on the other side of the arc from where his wants are. What we want to do and what we need to do are many times not the same, and are, in fact, often conflicting. But doing what we need to do is what gives resolution to a journey in which we have begun flawed – just surviving – instead of living it at its fullest.