When drawing anime clothes, one concept you want to understand is how folds work. Folds are the basic movements in which the clothing will be moving in. For example, if a fold is downward, more than likely the fabric causing the fold is being pulled in that direction. Add your shadows and highlights to your final picture then color in.
Sketch a basic outline in pencil of how the clothing will look on your model. Will your character wear a simple shirt, a robe or other long garment? If your character is kneeling, stretching, or hugging someone, be sure the clothing you add fits how the character is posed.
Add the major pull and stretch folds in the clothing to your basic outline. A pull fold is expressed when gravity pulls downward on saggy clothing like a robe. The folds that appear around the material that hangs down are called pull folds. A stretch fold depicts where on the body the fabric is using elasticity. An example of a stretch fold would be the area around the crotch when a character wears pants. Remember the posture in which you draw your character, this will help you identify where to draw your folds.
Add the minor pull and stretch folds. Using your colored pencils, add your shadows and highlights. If your fabric is blue, use the darkest blue for dark shadows and light blue for light shadows. Picture which direction the light is coming from. To give you a better visual, you can draw a light arrow from the direction your light source is projected and put the shadows behind your folds this way.
Color in your garment leaving some "white" light aspects for depth. This means to leave no color at all in this area to give it the appearance of light. Combine all your elements; working your way up from your darkest shadow, to the garment color, to light shadows and then your white. This will give your character's clothing depth and a more realistic look.
Sharpen your colored pencils with a hobby knife. Because these pencils are generally softer, you will lose more lead and they'll break easier in a pencil sharpener.
Draw your outline lightly; hard pencil marks are hard to erase and can leave indents in the paper.