1) Is it turning over freely? (or is it slow, or not turning at all?)
2) Check for spark.... (If you don't have the little $5 tester light, then just pull a plug and ground it out and see if you have spark) Note Make sure you fuel is turned off I would also recomend using a grounding wire instead of just trying to hold the plug against a ground...
3) Compression
4) Fuel are you getting fuel when the fuel is turned on... You should smell it when you crank the engine over w/o the plugs in it...
3 Things make the engine run Fuel, Compression, and Spark. You are missing something somewhere.