Shout on collar and cuff as pretreat, then launder. For deeper periodic cleaning, I use small squirt of Dawn (original blue) and a good 1/2 cup Hydrogen Peroxide in a large bowl of water, soak overnight. Go easy on the Dawn if it's in concentrated form - rinse, rinse, rinse... If there's a stain present that will set with heat, use cold water. Otherwise I'll use as warm of water as I can get away with and for white shirts that need serious attention, water off the boil.