The more detailed their description is, the better I can make it close to their vision. I have the ability to imagine scenarios vividly in my head and then translate them roughly into a sketch. I usually provide them 1-2 angles, maybe even more, and proceed when the client is happy with one.
As for the input, a race (human or creature), a pose, facial expressions, clothing and hairstyle is great as a base for a character creation, you can go further into the details with the color palette or inspiration image/character.
I have been asked this question a lot and my answer always is, asking for the characters personality, likes and dislikes, habits to fully understand the way the characters pose and expressions and of course making sketches out of it till the client is satisfied with their creation.
The process is pretty simple actually. First thing I must have is the character details, like outfits, pose and expressions. And then ask if they prefer kind of specific style. My favourite client is the one who provide picture references. And after all of that, I can estimate the cost and time.
To bring a client’s ideas to life, I employ a collaborative process. First of all, I start with detailed discussions and reference materials to understand their vision. I then create drafts and seek their feedback, ensuring alignment with their vision.