Set the dryer to the "Permanent Press" setting. Permanent press uses a moderate amount of heat, which will dry the T-shirt without overheating it and setting the wrinkles.
Set the dryer to only as much time as you need to dry the clothes. For example, if you are drying your white T-shirt by itself, you may only need to dry the T-shirt for 10 to 15 minutes. Overdrying the shirt can shrink it as well as set the wrinkles.
Remove the T-shirt as soon as the dryer stops. If you do not hear the dryer stop and the T-shirt is cool to the touch when you open the dryer, mist the T-shirt with water from a water bottle and restart the dryer for 10 minutes on the permanent press setting to loosen the wrinkles. Then, remove the T-shirt immediately.
Hang the white T-shirt immediately. This will prevent wrinkles from forming.