Short answer: drip your faucets when outdoor temps are expected to stay at or below freezing (32°F / 0°C) for several hours, and especially if you have older or vulnerable plumbing. Keep a slow, steady trickle rather than a full stream. Details to consider

• Indoor faucets: drip a small amount (roughly a pencil-lead width) to keep water moving through pipes most at risk of freezing. Do this on both hot and cold sides if your faucet handles allow, or at least ensure some flow through each pipe path.
• Outdoor faucets: these should be treated differently. Shut off the supply to outdoor hose bibs and drain them completely to avoid freezing and rupture.
• Temperature guidance: many guidelines trigger dripping when subfreezing temperatures are forecast for several hours, with stronger caution if temperatures dip toward 20°F or lower.
• Duration: you typically keep indoor taps dripping for the duration of the freezing conditions, then you can stop once temperatures consistently rise above freezing.
• Other protective steps (recommended):
  • Open cabinet doors under sinks to allow warm room air to circulate around pipes.
  • Insulate exposed pipes in unheated areas (basements, crawl spaces, garages).
  • Maintain home heating at a steady level; avoid large temperature swings.
  • If you’ll be away, set the thermostat to a minimum safe level (often around 55°F / 13°C) to reduce the risk of frozen pipes.

If you’d like, tell me your location or climate zone and whether you have any outdoor taps or single-handle faucets, and I can tailor the dripping rate and which fixtures to prioritize.