Machine wash at 40°C. Wash separately first time if strong colours. Do not tumble dry. Iron set to cotton.
Before washing undo all buttons, this will lessen the strain on the stitches holding the buttons on to the shirt. Also remember to remove any collar stiffeners before washing. Turn all shirts inside-out. Line dry or dry in an airing cupboard, this will lengthen the lifespan of the shirt. Do not tumble dry as the steel drum tends to wear out the points of the collar and cuffs.
Preferably iron while still slightly damp from the wash. A fine spray might still be required if the shirt has dried-out unevenly. In general lay the part of the shirt about to be pressed on a sturdy flat ironing board, using a dry iron (no steam) press the fabric until dry and crease free. The general order to ironing a shirt is: collar, cuffs, sleeves, yokes (shoulders), front panels and ending with the back panel. Then finally revisit any part of the shirt that may have creased while ironing.