Read the care label! If it says dry-clean only, or the mark is large, rush it to the cleaners.
Washable? Try cleaning fluid, spot remover, or petroleum-based pre-wash spray. Test in an inconspicuous area to be sure it's safe for the fabric. Place garment stain side down on paper towels and dab cleaner on stain using a paper or terry-cloth towel. Check paper towels underneath and move frequently so there's always a clean area under the stain to absorb ink. Let area dry and check it.
If ink remains, treat with pre-wash spray and launder. Before drying, check again. Still visible? Repeat steps