Will it even crank? If it won't, you have an ignition switch or lock cylinder going bad. If it does crank, just not running, then check to make sure fuel pressure is good and that the ignition coil is good. When exactly will it not start?
starter
take the battery terminals off and clean them and the battery mountings on the battery real good and reinstall.
Starter is not working.
take the battery terminals off and clean them and the battery posts real good with a wire brush and reinstall and see what happens.
this happen to me and turned out to be corrosion on battery terminal, clean them very good.
you need to hook up a good scan tool that will have the cam/crank feature.
no power? Try a Battery Jump-Box, Or Maybe the Starter is no Good? But if it dont Crank at all You are having some sort of Power Problem, all Fuses connected, Battery Terminals, etc..
Anywhere from 525 to 750 is good when buying a new battery. The more the better.
Sounds like a starter issue. Bad wire to the starter could cause it.
If you mean will crank, but no fire, then check for spark and fuel. If you mean will not crank, then check the wiring and the starter.
Starter? Wiring? Neutral safety switch?