it should start from dead cold on first try after 5-7 second Glow time, and should idle smoothly, Drive it around and see if it lacks power at any range. blows excessive smoke. misfire etc (misfire can be bad injection system or bad cylinder head), Check vibration etc.
drive backwards up a ramp and stop engine, put in first gear and release the clutch - the engines compression stops should be felt.
start engine whilst hot (needle in middle of gauge) - it should start with a glow of 1 second or even no glow.
Check blowby with a paper - If you see blow but it disappears on revving the engine - its OK
The engine should sound diesely on idle and go smooth at high revs - not sound diesel all the way