main thing i'd suggest you or anyone else should check is that if the car is what it is advertised to be. nowdays alot of 99's are facelifted to look like 2003+ models, also it woudl be a good idea to get the car jacked up and check the underside of it.
Suspension is usually overlooked in PK on 2nd hand car so it's always good to check it, also very often it's little things like cabin filters missing and fluids which are low etc.
It's always a good idea to check the plugs of the car as they can tell you alot about the condition of the engine, as can the oil.
99.99% of the time the transmission fluid is old and that's pretty much acceptable if the car has been driven aroudn 60000km as that is usually when it should be changed anyways.
best thing to do is to take it out for a drive and then compare it to a similar car which you now is good, and never settle for "yeh ashi hota hai" replies from dealers, it means that they are either trying to make a fool of you or that they don't know what htey are talking about.