Diff are weak, so play attention on whinge at 60-100km/h.
Rust is normally not a problem but a leaky boot / taillight may cause some dramas.
The dashboards and door trims rattle heaps. Not much you can do about this.
The gauges may get sticky and unresponsive. Sometimes you can increase/decrease speed by 10km/h and the speedo may not have moved.
Wirings of electronic items, esp. instrument cluster, ECU and cruise control, are know to develope broken solder joint and wires by the age.
Interior switches usually die and are a bit pricey to replace, such as rear defogger, hazards, air con switch.
Air Flow Metre are famous to break down and can cause problems that is totally irrelevant.
Injectors may need an overhaul at this moment.
Check when it last had a cambelt fitted, should be done religiously at every 100000, a worn cambelt also affects the timing and makes the car drive sluggishly, or flatspot in the rev range.
Exhaust Manifold are famous of warpping and leaks, listen for signs of a cracked exhaust manifold if the car doesn't have extractors fitted.
Bolts at exhaust manifold are famous for melting into thread and snap during removal, esp. on 3.0L engine.
P/S pumps leaks are common, but dun let it be to serious.
Rear panhad rod are likely bent if thrashed.
Squeaks and body flexing are common but can be fixed by a pair of sturt brace. But cars that are likely to pass their used by date are better avoided.
Chassis rail may be bent or damaged when running over bumps.
Brakes may be shockingly woeful and no easy, cheap and legal upgrade option exists.
Front ball joints are likely fail by this time, have a look on them.
Crank angle sensor, coolant temp sensor and o2 sensor can play up by this time, make sure they are working well.
Handbrake cables can sieze up, about $200 to replace with new ones and they'll last another 6-10 years.
The CV joint on the tailshaft wears after about 200,000km and may require replacement.
The centre bearing at tail shaft often dies and causes bad vibration on acceleration, easy and cheap fix.
Rear spring may be sagged if thrashed or towing overload trailers.
Suspension bushes front and rear will make it pretty floaty if they are flogged out, rears will also exacerbate a worn diff problem.
On manual cars listen for grinding on 2/3 , 4/3 gearchanges, 3rd gear components often get worn in these cars from owners resting their hands on the lever in 3rd round town.
Clutches aren't the most resilient thing a round, if its been abused the clutch will be on the way out.
Gearbox may play up so be sure to check it carefully. Series 3's electronic tranmission (after 1988) is not as bullet proof as the old one and are due for a rebuild if one isn't done before. May cost more than 1500 to fix for series 1 and 2 while over 2000 for series 3.
Make sure it has coolant and it is changed fairly regularly, same with 5000km oil changes, head and radiator are easily corroded if a suitable inhabitor is not used, expensive to fix.
Front shocks don't last long, have a look.
Accelerator cable may snap, so have a look.
Check the electric windows (if fitted).