Ketchup: Scrape off any excess, then apply a mixture of cool water and liquid dish soap (or hand soap if dish soap isn't readily available). For tougher stains, blot with white vinegar.
Ink: Spray heavily with hair spray or douse with rubbing alcohol and blot. Apply laundry detergent directly to the spot before putting into the wash.
Blood: Hold the fabric under cool, running water while rubbing it against itself. Avoid hot water, which sets the stain permanently.
Oils: Blot excess from fabric with a cloth or napkin. Work baking soda or cornstarch into the stain to draw it out. Wash with detergent. Or, blot with a sponge into which you've put a few drops of dish soap, as I've demonstrated previously.
Perspiration: Saturate the area with shampoo--preferably one for normal hair, as shampoos for dry hair contain extra conditioners--and then launder as usual.
Red Wine: Blot with club soda. The salt helps prevent permanent staining while the bubbles in the soda help lift the stain.
Coffee/Tea: Rinse with white vinegar or commercial stain remover. Blot.
Grass: Soak the area with white vinegar for an hour, then wash.
Chocolate: Scrape off excess with a dull knife or spoon. Saturate the spot with a solution made from a tablespoon of an enzyme detergent (like Wisk) and two cups of water. Let stand for 20 minutes, then rinse well.
Lipstick: Remove as much as possible with a credit card or dull knife. Dab with baby wipes, then rinse with hot water to dissolve the oils.
Chewing Gum: Freeze the gum with a wrapped ice cube, then peel it off the garment.