Dirt and stains typically consist of particles such as minerals from soil, protein and other organic matter from living things, or bits of black carbon. The particles are trapped on cloth fibers by grease and oil, which cannot be dissolved in water. By understanding the chemistry of stain removal, you can solve almost all stain problems.
Although you may need to try several different methods for stain removal, you should not combine different stain removers in an attempt to treat the stain. This can cause adverse chemical reactions, such as the formation of a toxic gas when you combine bleach and ammonia. To avoid this, thoroughly rinse and remove one stain removal treatment product before trying another one.
Check for colorfastness. Some harsher treatments for removing stains may change the color of the fabric you are trying to treat. There is nothing worse than a bright white spot on a red t-shirt where the stain remover removed the stain, but also the red dye in the shirt. Test for colorfastness in an inconspicuous area of clothing first.
Always check to make sure the stain is removed before you place it in the dryer. Nothing sets a stain worse than drying it in a dryer. If your stain removal method did not completely remove the stain after going through the wash, try something else. At the least, let it air dry instead of placing it in the dryer so you will have a better shot at removing the stain with another method.