Fill crankcase to proper level
Clean or replace air filter
Fill fuel tank
Drain gas tank and fill with fresh fuel
Connect wire to the spark plug
Replace the spark plug
Drain gas tank, fill with fresh fuel
Open choke fully and crank engine
Possible causes:
Low oil level
Dirty air filter
Out of gasoline
Stale gasoline
Spark plug wire not connected to spark plug
Bad spark plug
Water in gasoline
Over choking