To begin, observe real people and study how their bodies move and look in different positions. Also, collect references from existing comic books to get inspiration. Begin with simple shapes to form the characters' outlines.
First, you need to learn the basics of human anatomy and proportions. Then, practice simple poses and expressions. Start with rough sketches and gradually add details.
The key is to start with basic shapes like circles and lines to build the framework of the character. Study facial features and body language. And don't be afraid to make mistakes, keep practicing and you'll improve over time.