Car noise questions, answered straight

One question, one direct answer, then the details. Each links to the full guide.

• Is engine ticking serious?
• Why does my engine tick only when cold?
• Is direct-injection injector tick normal?
• Is it safe to drive a car that is making a clicking noise?
• Car clicking: is it the battery or the starter?
• Why does my car click rapidly when I try to start it?
• Is it safe to drive with a grinding noise?
• Brake squeal vs brake grinding: what is the difference?
• What causes a clunking noise when driving over bumps?
• Humming noise: wheel bearing or tire?
• Why does my car rattle only when cold and then stop?
• Why does my car squeak when I go over bumps?
• Why does my car only squeal when it is cold or wet?
• Can I spray something on the belt to stop the squeal?
• Why does my car shake in Drive but not in Neutral or Park?
• Is it safe to drive a car with engine knocking?
• Engine knock vs engine tick: what is the difference?
• Whining when you accelerate: transmission or something cheaper?
• Why does my steering wheel squeak only in cold weather?
• What does a clicking noise when turning mean?