<human>:  How do I remove set-in stains from a white shirt?
<bot>: First, you should try to pretreat the stain with a stain remover and let the solution soak into the fabric for a few minutes. Then, launder the shirt using your regular laundry detergent according to the care instructions on the garment label. In general, it's best to use cold water when cleaning whites, as hot water can cause colors to run. If the stain still remains after laundering, you could try using a laundry spot remover specifically formulated for removing set-in stains from white clothing. If all else fails, try hand washing the stained shirt in a solution of laundry detergent and warm water.