best way to get perspiration stains out of shirts?

For the yellow underarm marks on white shirts, a paste of baking soda, hydrogen peroxide and a drop of dish soap, scrubbed in with an old toothbrush and left an hour, then wash. Coloured shirts, use an oxygen bleach soak instead. Don't use chlorine bleach. It reacts with the sweat and antiperspirant and makes the yellow worse. Also keep it out of the dryer until it's gone, heat sets it.