Why My car wont crank?

First try shifting from Park to neutral and back to Park, if still nothing, Check the battery cables for corrosion and make sure they're tight, don't forget the one by the starter. If cables are ok, check battery voltage, it should be minimum 12.4. check voltage signal at the starter solenoid as you try to start it, if voltage is present and still doen't start, replace starter. If no voltage present, trace back to fuse, relay, neutral switch or ignition switch. Assuming ur not getting a security alert on the dash.