The best method for spot removal depends on the particular type of spot being treated. A spot should first be treated with a stain-cleaning agent, such as club soda, alcohol or baby powder, before laundering the item.
Treat the stain as quickly as possible before tossing the item in the laundry. The longer a spot remains unwashed, the harder it is to remove it. When treating the spot manually, apply the required stain-cleaning agent directly onto the stain. Blot the area gently and repeatedly with a soft cloth and cold water. Never use hot water to blot a stain, and don't rub the stain too forcefully, as this presses it into the fabric. As soon as possible after blotting, put the item into the washing machine, and run it through the proper wash cycle. Many spots can be removed with common household chemicals.
Kiwi Web's Stain Guide gives an extensive list of stains, including blood, ink, fruit juice, paint, oil and urine, that all have to be treated with different stain removers. For example, oxygenated bleach and hydrogen peroxide work on blood stains, while stains from fruit juice and other sugary liquids may require ammonia and wood alcohol, particularly if the stains have set in.