Well, first, you need to know the basic structure of the breasts. Pay attention to the proportions and the way they move. Also, look at references from real life or other artworks for inspiration. It's all about getting the curves and shading right.
To draw comic breasts well, you have to master shading to give them a 3D look. Also, consider the clothing or accessories that might interact with them. And don't forget about different poses and perspectives to make it more interesting.
It takes practice and an understanding of anatomy. Observe real breasts, study their shape and form. Start with simple sketches and build up detail gradually.