How do I remove the rear seat of a 72 Chevelle. I know I have to push down and then out or something of the sort but I forget exactly what to do...

Push down and back. Sometimes they pop right out but most times they are a real pain.

If it's like on a -69, you can see the retaining hooks through two slots at the bottom front edge of the seat (have to use a flashlight). Last time I took a back seat out, I used a flat prybar through these slots to push it out of the hooks.