this should apply to all cars regardless of age and make.

1. slam panel
2. wheel housing
3. floor pan (top and bottom, yes, crawl under the car or jack it up if you have to)
4. boot

as usual, you should be allowed to remove the floor pan carpet and interior trimmings (unless you damage them then you've gotta replace them). this will really help in finding trouble spots in a 2nd hand car.

check paint on all body panels for bubbles, cracks, dimples, or any imperfection. some minor dents or scratches can be ignored.

remove the boot carpet and check for signs of leaks (ie. watermarks) and dents or signs of imperfection. because sometimes, putty can be applied outside and painted back flush to the other parts of the particular panel but rarely do they car about the inside/covered up areas.

when i mentioned slam panel earlier, i'm referring to the spot welds that hold the slam panel and the left and right wheel housing. look for cracks or signs that the panel has been replaced, which could mean that the car has had a terrible collision from the front.

always stand back say 10 feet away and squat to look at the car. if you notice one side tilts (assuming the ground is rather level) question the owner/sale person whether there has been any major accidents. the tilt could be minor (ie. worn out shocks or spring) or major (chassis damage).

as for the engine and gearbox, look for any signs of oil/petrol leaks. if any are found (the slightest drop) request that repairs be made at no extra cost to you on top of the asking price for the car.

check the electrical system. bring a multimeter or voltmeter if you have one and check the voltage across the battery terminals. it should read between 13.5-14 volts under full load (ie. air con, radio, lights switched on). if it reads less than 13 volts, you should be warned that problems could arise later from your alternator.

any squealing sound usually comes from loose belts (timing/alternator) and screeching/whining from worn out bearings or a poorly lubricated air con compressor.

check hoses for visible cracks.

oh and one more thing, never rush into buying a second hand car no matter how good/tempting the deal is. always scrutinize the car until you feel your purchase is justified.

good luck in buying a 2nd hand car.

nightzstar,
the slam panel is the part where your radiator mounts are most probably situated. it also houses the locking mechanism for your bonnet. hence the 'slam' word used to describe the panel since you have to slam your bonnet in order to lock it.

nabelon,
you can use a long metal rod and place it on the alternator and air con compressor to identify source of vibration. or a worn out bearing.

as for exhaust smoke, it goes like so:

1. white smoke - coolant/water is introduced in the combustion chamber. most possible cause a faulty cylinder head gasket. worse case scenario, your cylinder block has cracked or developed a pin hole leak from rust or improper maintenance.

2. blue smoke - engine oil is introduce in the combustion chamber. most possible cause a worn out/faulty oil control ring (piston has 3 rings, top two are usually compression rings and the third is the oil control ring). or the bore of the cylinder exceeds the maximum allowable spacing tolerance between the piston and cylinder wall.

hope that helps.

happy new year.