I try to look for general apperance stuff like:
1.Does all the paint match?
2. Does the texture of the paint match...as in ...a fender lookin slightly different texturewise than the hood.
3. Do all the body lines..line up? It is virtually impossible to get lets say a hood and a front fender to line up properly after a car has been wrecked.One area that it a give away for a front end wreck is where the grill or front fascia area meets the hood..it should be a smooth transition..no gaping holes or uneven edges.
4.Look to make sure that gaps are equal at all points where body parts meet each other..If a door has a 1/8" gap at the top it should have an 1/8" gap all the way to the bottom.
As for mechanical:
1. Take the oil filler cap off check to see if there is a white substance inside the cap..if so walk away.
2. Make sure the vehicle is cold and have someone start it...while you stand behind it and look at the exhaust
blue smoke..oil ring on pistons are worn ...if it only smokes on start up.then clears up ...this means that the valve guides are going bad
white smoke= coolant(antifreeze) in the oil =cracked head or block or blown head gasket
It should idle smooth and have no hiccups/hesitations etc.
On the road test..run the shit out of it. If its gonna break you want it to break before you own it
In general bro look for things that would indicate a previous owner took good care of the car:
Few door dings would indicate he/she took the extra effort to park away from other cars in parking lots
Interior that is clean with no stains (granted 99% of stains can be removed at any reputable detail shop)
Most of the time if a car has been to a detail shop it will smeel too nice...the innerfenderwells might be freshly spray painted black..I could go on and on bro but this will get you started
Just so you know...my friend has been detailing cars for 15years and EVERY major dealership around him plunks down $80-$200 per car to him to get that extra buck out of it when they sell it.
Only because they know how much abuse he can cover up..lol. Best bet..buy from private owner..if your buying outright you would be a fool to buy from a dealer. ???