Assuming your battery is good. Check the fuse box(under hood) there is a relay marked STARTER. You should feel it click, when someone turns the key. If it doesn't click, switch the relay with another in the box(making sure they have the same number) and try again. If it doesn't click, there maybe a bad ignition switch or wiring to the fuse box. If is does click then the wiring from the fuse box to the starter is bad or corroded. Or maybe your starter is bad, or going bad. You can use a paper clip in place of the relay to test starter and wiring. By connecting 87a and 30 together(refer to drawing on relay). It should turn over. MAKESURE CAR IS IN PARK WITH PARKING BRAKE ON!!! You will be over riding all safety systems.