A screeching fan belt may just be noisy, and a touch of petroleum jelly on the underside may help. If the underside of the belt is cracked, frayed or glazed, replace the belt before it breaks. Carrying a spare belt may help you avoid towing charges if one breaks on the road.
Squeaks and groans can usually be remedied by lubrication, especially if you drive an older model without sealed joints.
Rattles and vibrations can easily be tracked down and eliminated by tightening the loose part that's causing them. If you can't find the culprit, have your mechanic play detective before any extra wear or damage can occur.