In general, greasy stains are removed using a grease solvent of the type normally known as dry cleaning fluids. You can get these at grocery stores and hardware stores and they should be used only according to directions on the label. Some are flammable, and virtually all give out vapors that are dangerous when inhaled in a enclosed area. The flammable type must not be used where there is open flame or danger of electrical spark is present.
Non-greasy stains usually are handled using some other type of solvent or remover: water, rubbing alcohol, liquid detergent, turpentine, acetone or amylacetate. A lot of stains will actually be a mixture of greasy and non-greasy elements; hence successive treatments with both types of solvent will be involved.
If a fabric is not washable yet the stain needs treatment with water, use rubbing alcohol instead. Test the effect of the alcohol on one corner of the fabric. Alcohol can be used also on non-washablefabrics rather than water to flush out detergent when this treatment is needed. The alcohol dries faster and is less likely to induce shrinkage or other damage. It should be thinned with 2 parts of water when used on acetate fabrics.
Use grease solvent and work from the back side whenever possible. This would do the least possible damage to the fabric. To prevent spreading the stain, always apply sparingly and work from the center out towards the edges using light brushing strokes. Do repeated light applications, instead of one or two large ones. Spread the solvent to an irregular line around the edges and feather out the strokes to minimize the likelihood of forming a ring. If the fabric won't be harmed by it, a ring of absorbent powder also can be sprinkled around the stain prior to applying the solvent.