Button the dress shirt fully, including the collar and cuffs if applicable
Put on the pants and unzip or unbutton them
Tuck the shirt into the pants evenly all the way around
Pull the shirt down snug so there is no excess fabric blousing out
Smooth the front, back, and sides with your hands
Fasten the pants while keeping the shirt tucked in
Check the sides and back in a mirror
Adjust the shirt so the hem sits flat and even inside the waistband
Use a belt to help keep the shirt in place
Recheck after sitting, standing, and moving around