Won't start

if it turns over (cranks) but doesn't start you can check for spark , you can get a spark tester or pull a plug wire put a wire in it and see if it arcs on an engine ground , check for fuel , when you turn the key ,key on/engine off , you should hear the fuel pump charge the system , a faint "whirrrrrr" or a pressure gauge on the valve on the fuel rail , check injectors for pulse with a noid light , there's probably a relay in the fuel pump wiring and various ignition relays , exciters and amps , your experience may vary

some vehicles are particular about spark and fuel pressure ,they must be correct , just having them isn't always good enough