a. Discard old gas and use new fresh ones;
b. Is gas being pumped out and getting into carburetor? If not, blow air into the tank to prime the carb.
c. Still no gas flowing, check if fuel filter is clogged or dirty; replace if necessary. It costs less than 3 dollars.
a. Do you have spark? To check for spark, remove the spark plug, place near a ground point (with the plug inserted into its cable), crank the engine and check if there is spark.
b. No spark, replace spark plug. About 3 dollars.
3. Ignition coil: borrow or buy a new ignition coil.
There are other tests but just do the above first. Your engine may just run.