Change the different painting to heavy In the sketch: In the sketch drawing paper with different drawing strength in just the basis of the large outline for a deeper layer of shaping, drawing different variations, the color of heavy can create a deeper dark and shadows, has been to obtain a deeper sense of three-dimensional.

Use the intersection change of different lines: Use parallel lines, cross lines and row lines to add shadows, texture and depth of different colors.

Use different levels of drawing pencils: From the harder H grade to the softer B grade, the different application of each grade will have different painting results, from light to deep, layer by layer, gradually increasing the depth of the painting and making the picture richer and more three-dimensional.

Blending Tools: Incorporate blending tools into your process. Blending stumps, tortillons, or even a soft tissue can help you seamlessly blend and soften pencil strokes for smoother transitions between tones. 

Negative Space: Pay attention to the negative spaces around your subject. Defining and shading the background areas can enhance the focal point and create a more dynamic composition. 

Reference Points: Utilize reference points and lines to maintain accurate proportions and angles. These guiding marks will aid you in capturing the true likeness of your subject. 

Erase Strategically: Don't hesitate to use your eraser strategically. It's a valuable tool for refining edges, adjusting highlights, and correcting minor mistakes. 

Practice Regularly: Like any skill, sketching improves with practice. Dedicate time to regular sketching sessions to enhance your techniques and develop your own unique style.