On my baby's clothes I use Dreft Stain Remover right away. You have to react fast. You will be take any stain out while the stain is still wet. Here are some additional great tips;
(Shout, Spray 'n Wash)
All-purpose stain removers, particularly good on greasy stains.
Also called dry-cleaning fluid, these remove oily, greasy stains. Safe on nonwashables. Use only on dry fabric, in a well-ventilated area. Air clothes after using.
(Biz, Era Plus, Wisk)
Also called enzyme cleaners, these detergents contain enzymes that "eat" protein stains, like grass, blood, and egg yolk. Apply directly to damp fabric, or dilute in water, and then soak clothes. Use cold water when treating blood stains. Wool and silk are proteins, so digestants should never be used on these fibers.
(cornstarch, talcum powder)
Sprinkle on fresh grease stains, wait about ten to fifteen minutes, then scrape off. Then you can treat the stain.
A mild, clear liquid dishwashing detergent is an effective all-purpose cleaner. Apply it straight, wait five minutes, then flush or dab with water.
Remove the color left behind by stains with mild bleaches, like lemon juice; white vinegar (mixed 1:1 with water); 2 or 3 percent hydrogen peroxide; or ammonia (2 parts water to 1 part ammonia; do not use on wool or silk). Use a cotton swab to dab the bleach, or place paper towels under the fabric, and use an eyedropper to flush the area with the proper bleach. Chlorine bleach, diluted with water, is a last resort.
Effective at breaking down some stains and evaporates without leaving a residue.
For greasy stains, like tar. Air clothes after using.
Available at drugstores, it is particularly good for ballpoint ink.