How do start a 1994 Chevy cavalier when the battery and alternator is good but still wont turn over?

First, make sure your all of your electrical connections and fuses are good. (battery cables are not corroded and cable to starter and ground are good) If they are good, it sounds like you either have a bad ignition switch or starter. You might try having someone turn the ignition switch to start position while using a multi-tester to see if you are getting power to the starter. If you are getting power to the starter, and it won't engage, chances are you need a new starter. If you do not have power to the starter, you might have a bad ignition switch. In certain circumstances you might try tapping on the starter with a hammer while someone is turning the ignition switch to see if it will engage. If it will, I would look to a bad starter. I have found that a majority of the time, a starter is the problem, not the ignition switch. Hope this helps.