I have a 1997 Expedition, which badly needed a tune up: the motor was shaking. I changed the plugs, which stopped the shaking; two days later the truck won't start. The battery is hot and the lights work, but it won't even make the clicking sounds. Where do I go from here?
As Dan says in the comments, have you tried a different battery? If you have power to the lights, you should have power to the starter, but a poor battery may not give enough power to fire the solenoid.
The other possibility is that the shaking you have mentioned has caused one of the leads going to the starter to fail. There should be two cables attached to the starter, a big one from the battery and a small one from the ignition switch. The latter is often quite thin and so could possibly fatigue and snap at the connector. You can test this by disconnecting it at the starter end and using a multimeter to see if it gets 12v when an assistant turns the switch to 'start' (or by the not-recommended method of shorting the connections on the starter together so it gets power from the main battery feed.)