Has it got enough fuel? Dont trust the gauge, put a gallon in.
Immobiliser - is the light flashing?
Cam belt broken - remove oil filler cap, if you can see cams are they turning when the engine is cranked? If you cant see, remove cambelt cover and check.
Fuel pump - can you hear it priming when you turn on ignition? Get a fuel pressure tester on it.
Is the battery fully charged? It might be cranking, but not have enough power to start. Does it sound different when cranking?
free, November 2009