So you have a stain and you either don't know what caused it or what it is on your favorite clothes. Well here is a few tips for getting that stain out.
First you need to rinse the stain in cold water. Treat it with a pre wash either spray or soap. Then rinse again. Now wash the item in a chlorine bleach or an all fabric bleach, in water that is at the temperature that the manufacturer recommends, add extra detergent to the wash.
Let the item air dry. If the stain is still there then soak again for half an hour in cold water, sponge it with a cleaning solvent letting it sit for 5 minutes and then rinse again.
What you are doing here is a system of elimination and it should work. If not repeat the above again.
Other
ideas:
Try out lining the stain in chalk. If the stain is any type of oil the chalk will absorb the oil and grease.
There are times when a piece of break rolled up in a ball will take out stains in your laundry.
Adding four or five cups of ammonia to your wash will fight stains that you don't see!