Car won't start

First I would check is to see if you are getting 12 volts to the starter on the wire coming from the ignition switch(it is the small wire connected to the s terminal on the starter(normally connected with a small nut on a post or an electrical plug with a medal blade. This wire will only have 12 volts on it when the ignition switch is in the start position. disconnect that wire from the starter and connect the red lead or + lead to the wire that you just took off. Then connect the black (-) lead to a good ground(medal part of the car). With the meter hooked up try and start the car and observe on the meter what voltage is on it while attempting to start it. If you are not getting 12 volts at that wire then you either have a bad wire or the ignition switch is bad.