To be a designer, don't just draw. But, must have a high idea and creativity in designing a shirt or clothes.
The point is you are not drawing a realistic body shape, but a blank canvas to show illustrations of dresses, skirts, blouses, accessories and all your creations. Add colors and other details such as lace, lining, and buttons, to help you describe the ideas that are in your mind

1. Prepare your equipment
2. Determine the pose for your sketch
3. Use another method in drawing croquis

Paste the material you are using next to your design image, so that people see the fabric you are using.

thanks.