When you're developing a character, consider their voice, movement, body language and mannerisms. Discover their motivation and objectives, and research social, cultural and historical contexts.
If your character was an animal or bird, what would they be? Experiment with animal characteristics in body and voice. Try being 100% animal and then move gradually back to human, with only 10% of the animal present in your acting. You may discover gestures and mannerisms that work well which you can incorporate into your characterisation.
Search for inspiration
Is the character like anybody you know or can you take inspiration from elsewhere? If other actors have played similar roles, look carefully at how they did it. It’s a good idea to have a clear vision in your head of what you want to achieve. Sometimes even a picture that you think looks like your character can help.
Character motivation and objectives
Your character’s motivation is what drives them or what they would like to achieve. For example, a character may behave in a childish or argumentative way but their overall motivation is to be noticed and get attention. Look at Naturalism and Stanislavski to learn more about motivation.
Within a scene a character may have various smaller aims, which are called objectives. Take a look at this clip of actors from Shared Experience working on conflicting objectives with director, Polly Teale in a scene from the play, Speechless.