Draw a basic torso shape
Sketch the neckline
Add the shirt collar on both sides
Draw the collar stand under the collar
Extend the shoulder seams
Draw the sleeves or armholes
Outline the shirt body
Add the front opening
Mark the button placket
Draw the buttons
Add the pocket if desired
Refine the collar points and folds
Clean up the sketch lines
Ink or darken the final outline
Add light shading and fabric folds