get as much of the maintenance history on it as possible. That way you know what has been done,and what will need to be done.
In general you check:
Hoses (Cracked/bowed/rotting/etc.)
Belts (cracked/cut/etc.)
Wires
Start it up (hear an misfires? and odd sounds?)
I take every car i plan on purchasing to a mechanic for an inspection. Should run mayb $40