I keep a large bucket by my washer with water and a generous scoop of Oxi Clean. Whenever I come across an article of clothing with a stain, I toss it into the bucket and give it a quick stir. (I have also used Biz and that works well, too.)
The next morning, after soaking overnight, when the laundry is started, the contents of the bucket are poured into the washer and the load is done as usual. (I do not pour the bucket into dark loads.)
The stains are always gone! This even works with newborn poop stains that have gone through the dryer! If you know newborn poop stains the way I know newborn poop stains, you know that stuff is The Grandaddy of All Stains. Talk about staying power! And newborn poop stains that have gone through the dryer? Well, let's just say I've tossed a few cute little outfits before I heard about this bucket method.
If you have tough stains, try this!