you need three things for a car to start. fuel, compression and spark. with these three, it may not run well, but it will run. So start the process by checking to see if it is getting fuel to the motor. you don't say if it is a carb which is easy to check for fuel,it's tougher if it is fuel injected. If you have fuel, check spark at the spark plug. WARNING: new high voltage ignitions will shock you right thru a spark plug wire. DO NOT HOLD THE WIRE TO CHECK FOR SPARK. either buy a spark plug tester at the auto parts store for under $20.00, which is the best way to do it, or, with the ignition off, pull a sparkplug wire off one of the spark plugs, place another sparkplug into the boot of the wire, ground it against a good ground on the car (like an exhaust manifold bolt)without having to hold it, and have someone try to start the motor while you watch for a spark to jump across the bottom of the plug. If it sparks, you have no problem there, move on. Lastly, check for compression with a compression gauge at each cylinder. It has to be one of these three. I'd bet on a fuel problem. IE: fuel pump, plugged fuel line or filter. Second bet would be ignition problem preventing spark
Good luck