In her book, WRITING FICTION, Janet Burroway says about knowing what your characters want: "It is true in fiction, in order to engage our attention and sympathy, the central character must want and want intensely. The thing that character wants need not be violent or spectacular. It is the intensity of the wanting that counts. She may only want to survive, but if so she must want enormously to survive, and there must be distinct cause to doubt she will succeed."
Want can also be expressed as wish, need, or hope. It can take the form of a strong emotion, such as a mother being overprotective of her son. What makes the mother overprotective is the motive.
Motive is defined as: an emotion or desire or need that incites a person to act. Motive is what gives characters flesh and blood rather than being a mere description of hair color, dress, mannerisms, and occupation.
Let's look at Cinderella. What does she want? She wants to marry the prince. What motivates her? She spends all day cooking and cleaning and getting abused by her step-family, so she wants to escape. Another example:
Isabel wants to get even with her past by distancing herself from her family. She thinks that in doing this she won't go hungry, either psychologically or physically. What is her motivation? Her mother left her when she was 12, her father didn't care about his daughters, and she often went hungry because he didn't provide food for his family. This is what motivates Isabel to ultimately move away from home and buy a diner where she is surrounded by food and customers who love her on a daily basis.
Sometimes different character's wants clash. That adds drama and conflict to a story. Isabel's sister Hope wants to bring her family together. What is her motivation? The same reasons Isabel was motivated to leave home and put distance between herself and her family. Your character's motivations can be the same while the wants are different. Just like real life people, different characters handle the same situation differently.
To understand more about motives and needs, probe your own life. Start with the most basic human need, love. We want (or need) love. What does needing love feel to you? How does it manifest in your actions and feelings? When you create your characters, ask them the same questions.