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.
Speaking of detectives, be sure you stick to the facts when reporting symptoms to your mechanic. If you tell him or her that you know what the problem is, and ask for specific repairs, you may end up paying for work you didn't need. So just supply a clear description of what happens ("There's blue smoke coming from the tailpipe"); when it happens ("The idle's rough at stoplights"); and where the trouble is located ("There's a loud rumble under the front seat").
Highway 1 contributor Deanna Sclar is the author of "Buying a Car for Dummies" (1998) and "Auto Repair for Dummies" (1999) from IDG Books.