I must admit, our whites don't remain very white for long when they're in the hands of two grubby explorers who prefer hands to utensils.
Exhibit A: The status of a white dress at 9:22am.
Exhibit B: Nappies inserts after a lemon juice soak, wash and dry.
For spot removal around necklines, underarms and other places: pour lemon juice (fresh or store bought- whatever you have on hand) over the stains, rub table salt into them and leave to dry in full sun for up to 7 hours. Then wash as normal.