When I turn the key in the ignition the car won't start and the starter makes no sound. It has a new battery and a new alternator. What I can I do besides set it on fire?

CHECK STARTER RELAY TO SEE IF ITS GETTING POWER.IF YES.RUN HOT WIRE FROM RELAY B+ TERMINAL TO STARTER POSITIVE TERMINAL.IF STARTER RUNS THE RELAY FAULTY.IF STARTER DONT RUN ITS FAULTY.

You may have a bad starter, the best to determine this is by testing for power at the starter,also the battery is new but is it still good and fully charged, you may what to make sure battery is fully charged first, then test starter with a test light, there are two connection at starter, one is a battery cable this has power at all times then the small wire,this should have power when key is held in the crank postion,have someone hold the key while you test. if theres power at both connections then starter is bad, heres a diagram to show you where to test starter.