Short answer: drip faucets enough to keep water moving when outdoor temps are at or below freezing, and continue until temperatures stay consistently above freezing. What to do

• Drip rate: aim for a slow but steady drip—roughly one drip per second is a common target, or the width of a pencil lead on a single stroke. For single-handle faucets, let both hot and cold water flow so water moves through the pipes.
• How long to drip: keep dripping as long as temperatures are at or below freezing. If you expect brief dips, you can start dripping before the coldest period and stop once it rises above freezing for an extended period.
• Outdoor faucets: shut off and drain outdoor hose bibbs before a deep freeze, rather than dripping them. If you must drip an outdoor faucet, use a covered, insulated faucet cover to reduce heat loss.
• Indoor pipes in unheated spaces: open cabinet doors under sinks on exterior walls to allow warm room air to reach the pipes, and insulate exposed pipes with foam sleeves or insulation wrap.
• Consider alternatives: where possible, insulate exposed pipes, maintain a stable indoor temperature (even when away), and repair any gaps in your home's envelope that let cold air reach plumbing.

Tips to reduce waste

• Only drip visible hot or cold water through each connected faucet; ensure both sides are active if only one is dripping, to protect both hot and cold lines.
• If you have well-insulated or heated-space pipes, you may be able to use a gentler drip rate; adjust based on how cold your nights get and how quickly lines are freezing.

Common caveats

• Do not rely on dripping as the sole protection if you have known vulnerable areas or severe cold for extended periods; prioritize turning off and draining outdoor lines and insulating indoor pipes.
• Drip practice varies by climate and home. In some regions, professionals recommend closing and draining outdoor lines entirely, and in others, a controlled drip is sufficient. Always consider local guidance and your home's specific plumbing layout.

If you’d like, tell me your location and which faucets you’re worried about (indoor vs outdoor, exposed vs insulated), and I can tailor a precise drip plan and duration for your situation.