Best way to check the condition of an engine?

[TRDTom]

I am looking at buying a new car and I was wondering how I can make sure that the engine is good. Do you guys have any suggestions?

 

[Xterramods]

Take the oil filler cap off and check for excessive smoke (have a look on YouTube). If you can, take it to a mechanic for a compression test and listen closely for any knocks