How often should I clean my dryer vent?

Every year, minimum — and every 6 months if you dry more than 5 loads a week or have a long vent run. Clogged dryer vents are the #1 cause of house fires attributed to appliances (per the U.S. Fire Administration), and they double your dryer's electricity use before they get to that point. Both problems, one $150 cleaning solves.

Why is my washing machine shaking so violently on spin?

A violently shaking washer is either unlevel, has a load unevenly distributed, or (on front-loaders) has never had its shipping bolts removed. Front-loaders shake worst when the four rear shipping bolts weren't taken out at install. Check for those first — they're marked in the manual and often overlooked.