Soap residue on clothes: Make sure you’re using a detergent designed for high efficiency machines if you have that type of machine. If that isn’t the issue, make sure that you’re putting your detergent in at the bottom of the tub, especially if you use detergent pods. If all else fails, add an extra rinse cycle.
Fabric pills: These are little balls of evil. The best way to banish them is to limit which fabric types you wash together. It’s all about fiber length: keep your fleece blankets away from your bed sheets, for example.
Bleeding colors: It might seem okay to wash everything at once, especially if you’re using a ginormous-capacity laundromat machine, but be careful. Separate items by color and use the appropriate temperature.
Mildewy and moldy washers: Consumer Reports cites this as an issue with front-loading machines, mainly because we tend to close the front door so things look nice and curious children and pets don’t climb inside. That’s not such a good idea, though: leave the door open when possible to let the tub dry out. If you have mold issues, periodically run the machine empty on a hot-water setting, or an empty load with some bleach.
4 common laundry problems and how to solve them [Consumer Reports]