Make sure the gearshifter is all the way in park. I used to have a 1995 T-Bird that wouldn't start on me one day. Spent hours trying to find out why it wouldn't run. Turns out the gear shifter wasn't all the way in park. It was far enough forward to put the transmission in park, but not quite far enough forward to engage the interlock switch and let the car start.

Jiggle the gear shifter, make sure it's pushed all the way forward, and try starting it again.

No doubt your 21 year old car needs new battery cables. As they age they gain electrical resistance and eventually burn out.

Only the negative cable is hot? Clean and tighten the terminal connection.

check the positive side for clean/good contact.

Try jump starting?

Starter solenoid okay?

regulator okay?

You have a lot more work to do.