Treat collar stains before laundering a dress shirt. Apply a laundry pre-treatment spray as specified on the label and hand wash the collar under cold running water or launder it in the washing machine.
Wash white shirts one or two days after wearing them. If they sit for too long, they will begin to turn yellow from bodily oils.
Launder good shirts per the care instructions on the label. Use an appropriate amount of detergent and launder the shirts with like colors. For white or light colored loads, wash in hot water. For dark loads, wash them in cold water.
Hang dry shirts or dry them on a low to medium setting in the dryer, not on high heat. If possible, take the shirts out when the are slightly damp to iron them immediately. They will dry the rest of the way while ironing.