If the interior lights are on, and you try to start it, do those lights dim indicating that the starter is at least drawing current? Or, can you measure the battery voltage at the battery while someone turns the key? Does the voltage drop? If you have a meter, crawl under the car (raise and support properly if you need more room) and measure the voltage at the battery terminal Also on the terminal on the selenoid while someone turns the key.
If you do not have a meter, you could try this. Do this only at your own risk, and if you have any concerns at all, do not attempt it. If you do it wrong, you could at the very least cause a severe burn by shorting battery voltage to ground.
If you have a short jumper, attach one end to the selenoid terminal. Then, take the other end and briefly touch it to the battery terminal on the starter. If the starter starts to run, the starter and selenoid are likely good, and your problem is in elsewhere, swtich, wiring, etc.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.