Have someone stand behind the car while you drive straight ahead. The front and rear wheels should line up. Blue smoke from the tailpipe means the car is burning oil - a costly fix. Billowy white smoke is serious as well. It means water is entering the combustion chamber.
White vapor emerging briefly from the tailpipe on a cold morning is nothing to worry about.
Comfort and noise. Suspension work may be in order if the car bounces or rattles over rough roads at moderate speeds. Sputtering sounds from beneath the chassis indicate an exhaust-system leak.