Check the starter solenoid. If you cross the 2 big posts and it cranks the solenoid isn't the problem. If you touch the big post to the small post on the solenoid and it cranks, the solenoid is the problem. MAKE SURE VEHICLE IS IN PARK BEFORE CHECKING STARTER SOLENOID!
If solenoid isn't the problem, check the neutral start sensor on the side of the transmission.

