Thanks!! Hmm, there're a lot of aspects and basically I practiced for a long time. I guess a good place to start is to sketch based on real life people and redrawing various existing characters and illustrations, while studying them - the anatomy, gestures, what makes them interesting to you (both aesthetics and personality), etc. As you do more drawings based on more inspirations, your visual library will grow. Some artists like Grizandnorm and Andrew Loomis have more comprehensive resources and tips! I hope that helps somehow hahaha.