Well, to draw manga eyebrows, you need to consider the character's expression and personality. Use light and smooth lines for a more natural look. Also, pay attention to the thickness and length based on the style you want to achieve.
Start by understanding the shape and position. Observe different manga styles and practice simple strokes. It takes patience and lots of practice.
The key to drawing manga eyebrows is to have a clear idea in your mind. Sketch lightly at first, then build up the intensity. And don't forget to add highlights for a 3D effect.