There are a few things I keep in mind when designing a character. I try to bring them to life in a similar way that I think an actor would a role. I imagine the character's life and what it would be like, as if I have become the character. How it would shape me and the setting I'd live in. After I feel comfortable with my new self, I analyze how it would be communicated to others, not only the audience, but anyone else who may work with this character.
Putting yourself into the character's shoes is the emotional connection that can really boost the authenticity of the design and make it more appealing to an audience. The same way we don't feel a deep connection with a brick wall, a flat character will just take up space. No fun. Also, once we are in the spirit of the character, it frees us to experiment and try different ideas, such as clothing, tools, environment, vocabulary, etc. We get to have fun with a new life while making the design so play and make it impactful!
Secondly, communication is essential to reach two groups: the audience, and any others that may work with the character. Obviously, the audience needs to feel, whether it is positive or negative. If it provides people with an emotional response, then it's working well! Other than the audience, such as other artists, the pipeline, or the client, if this design is passed along and they can't grasp the concept, then it is a weak link in the chain. Yikes. If the person receiving the blueprint can't make any sense of it, then how can he work with it, or even make it better?
These are just two of the main things that I strictly keep in my mind when making designs. This is my method for now, but I am always ready to change or add new elements in the future, as I learn, meet superior artists, and taste discovery. Perhaps then I can make a Part II of this! If any of you have specific techniques that you'd like to share, I'd enjoy reading them. =)
Thank you and have a good day!