Arm yourself with a pair of red neon in line spark testers and a can of starting fluid.
Fit the spark testers ( you will need 2 of them ) and go mow.
The instant it stops , set the controls to the starting position, jump off and crank the engine.
If you see erratic sparks, different sparks each side or no sparks at all then as above you have a coil / wiring problem
If you see a good & constant spark the give the engine a short shot of starter fluid.
If it starts right up and runs on the starter fluid then you have a fuel problem.
As I have no intention of writing a complete service manual, get back to us with the results & we will tell you how to close in on the diagnosis to find your problem.